01 Oct 2026

Glossary of Psychological Terms

Definitions of terms used in psychology, psychometric testing and occupational assessment, organised alphabetically.

Obedience

In social psychology, a term used specifically for conformity to the demands or instructions of an authority figure, as distinguished from more general conformity to peers or social norms. Studied most famously in Stanley Milgram's experiments on obedience to authority.

Object blindness

See agnosia — the inability to recognise or interpret objects despite otherwise normal sensory function.

Object cathexis

In psychoanalysis, the investment of psychic energy (libido) in a chosen “love object,” typically involving the redirection of that energy from a purely sexual aim toward a broader, non-sexual attachment. See also: cathexis.

Object constancy

The tendency for a familiar object to be perceived as retaining the same fundamental properties even as the perceptual conditions around it — lighting, position, distance — change. See also: colour constancy.

Object loss

In psychoanalysis, the loss of love, attachment or connection to a valued external person or “object,” often a central concern in understanding grief and depression.

Object permanence

According to Jean Piaget, the understanding, acquired during the sensorimotor stage of infancy, that objects continue to exist even when they can no longer be seen, heard or otherwise perceived. This understanding is generally well established by around 18 to 24 months of age.

Object-relations school

A group of British psychoanalysts, including Ronald Fairbairn, Melanie Klein and Donald Winnicott, who emphasised the formative importance of emotional relationships during the first two years of life. The “object” in question is typically the infant's mother, or more precisely the infant's internal perception and mental representation of her.

Objective

Describing something understood to exist independently of oneself, and capable of being observed or verified by others in the same way. Contrasted with subjective, which refers to a purely personal, individual experience or viewpoint.

Observational learning

Any form of learning that occurs through watching another person's behaviour, rather than through direct personal experience or reinforcement — encompassing both deliberate modelling and simple copying or imitation.

Obsession

A persistent, anxiety-provoking thought or idea that intrudes on a person's mind and proves difficult to dismiss or control. Compare with compulsion, the behavioural urge that often accompanies it.

Obsessive-compulsive neurosis

A condition in which a person is not only preoccupied by certain intrusive ideas (obsessions) but feels compelled to act on them, often through repetitive, ritualised behaviour such as excessive counting or handwashing (compulsions). Psychoanalytic theory interprets such behaviour as an unconscious attempt to relieve underlying guilt — as with Lady Macbeth's compulsive hand-washing in Shakespeare's play. Now generally referred to as obsessive-compulsive disorder (OCD).

Occam's razor

A principle, attributed to the medieval philosopher William of Ockham, widely accepted as a cornerstone of scientific reasoning: when several competing explanations for a phenomenon are available, the simplest one that adequately accounts for the evidence should be preferred. Lloyd Morgan's canon, applied specifically to animal behaviour, is built on the same underlying logic.

Occupational psychology

See work psychology — the branch of psychology applying psychological principles to the workplace.

Occupational therapy

A therapeutic discipline, often used alongside psychotherapy in hospital settings, that engages patients in purposeful, useful tasks and activities to support physical recovery as well as self-esteem and a sense of personal worth.

Ockham's razor

An alternative spelling of Occam's razor.

Oestrogen

A hormone secreted during the period of oestrus, when a female animal experiences heightened sexual receptiveness. The relationship between oestrogen levels and sexual behaviour in humans is considerably less direct and simple than in many other animal species.

Old brain

The most evolutionarily primitive part of the human brain, situated beneath the cerebrum, responsible for basic reflexes and fundamental bodily regulation, and containing structures such as the limbic system.

Olfaction

The sense of smell, and the perceptual and neural processes involved in detecting and identifying airborne chemical odours.

One-trial learning

Learning that becomes established after only a single exposure or practice attempt, rather than requiring repeated trials.

Ontogeny

The developmental history of a single individual organism, from conception through to maturity. Contrast with phylogeny, the evolutionary history of an entire species.

Operant conditioning

A form of conditioning, introduced by B. F. Skinner, that shapes behaviour by reinforcing or punishing responses an organism spontaneously produces on its own, rather than eliciting a response to a specific paired stimulus as in classical conditioning. The emphasis is on the organism actively operating on its environment: a rat that happens to press a bar and receives a food pellet will gradually learn to press the bar deliberately to obtain food. Through carefully structured schedules of reinforcement, animals can be trained to perform remarkably complex sequences of behaviour.

Operational definition

Defining an abstract concept in terms of the concrete, observable procedures or operations used to measure or study it — for example, defining “hunger” as the number of hours since last eating.

Opinion leader

A term from sociology for a person of standing within a particular group whose views are especially respected, and who can therefore shape the opinions of other group members. See also: two-step flow of communication, the theory describing how mass-media influence often reaches most people indirectly, via such opinion leaders.

Oral stage

In Freud's theory of psychosexual development, the first stage of infancy, in which the infant's primary source of pleasure and preoccupation is the mouth and its functions (sucking, feeding). As with all of Freud's stages, excessive frustration or excessive gratification at this stage may leave an adult fixated on it, potentially producing an “oral character” marked by a strong need for oral stimulation through eating, drinking, smoking or talking — sometimes expressed, Freud suggested, through sharp or “biting” remarks.

Organisational culture

A concept drawing on both anthropology and psychology's use of “culture”: not just the shared beliefs, values, attitudes and expectations held by an organisation's members, but also the largely unquestioned assumptions embedded in its traditions and established ways of doing things.

Organising tendency

A term used in the study of perception for the way innate physiological processes combine with individual experience to actively structure and organise our perceptual world, rather than simply registering raw sensory input passively.

Orienting reaction

A term from physiological psychology for an animal's automatic behavioural response — typically shifting attention, posture or sensory orientation — to deal with a new or unexpected stimulus in its environment.

Out-of-body experience

The reported feeling of a free-floating, disembodied self, detached from one's physical body — sometimes described by people who have survived a state of clinical death, who often report the sensation of looking down at their own body, for instance lying on an operating table.

Outer-directed

A term introduced to sociology by American sociologist David Riesman for people who respond to their society mainly by conforming to prevailing social norms, seeking approval and popularity from those around them. Contrast with inner-directed.

Overachiever

A person whose accomplishments exceed what would typically be expected of them given their apparent ability; sometimes used, particularly in education, to describe someone perceived as trying harder than their natural aptitude alone would predict. Contrast with underachiever.

Overcompensation

Exerting a level of effort well beyond what is actually needed to overcome a difficulty or resolve a perceived shortcoming — often discussed in connection with attempts to counteract an underlying inferiority complex.

Overconforming

Describing a person who adheres excessively and rigidly to the demands of authority or the conventions of prevailing social norms, well beyond what the situation actually requires.

Overdetermined

In psychoanalysis, describing a phenomenon — particularly the origin of a neurosis, or the meaning of a dream — that has more than one underlying cause operating simultaneously. Since most neuroses and dreams are considered overdetermined in this sense, psychoanalytic interpretation typically looks beyond any single, simple explanation toward a more layered, multi-causal account.

Overlearning

Continuing to practise or rehearse a skill or piece of material well beyond the point needed for basic, adequate mastery. Overlearning is not generally considered harmful — unlike some popular assumptions, it is not thought possible to “learn something too well.”

01 Oct 2026

Glossary of Psychological Terms

Definitions of terms used in psychology, psychometric testing and occupational assessment, organised alphabetically.

N Ach

An abbreviation for need for achievement — see that entry.

N Aff

An abbreviation for need for affiliation — see that entry.

Naive subject

In psychology generally, a research participant unfamiliar with the specific experiment they are taking part in; in social psychology specifically, a participant who has been deliberately misled about the experiment's true purpose. In conformity research, for instance, telling participants upfront that the study is measuring how much they conform to group pressure would defeat the purpose, so a cover story is used instead, with the true purpose revealed afterward during debriefing.

Narcissism

Named after the Greek myth of Narcissus, who fell in love with his own reflection: excessive self-love or self-preoccupation, to the exclusion of genuine interest in others. In psychoanalytic theory, an early stage of psychosexual development in which the infant's own self is the primary object of libidinal interest.

Narcolepsy

A neurological disorder characterised by sudden, uncontrollable episodes of falling asleep, regardless of the situation or the person's intentions.

Narcosis

A state of stupor or deep unconsciousness induced by drugs.

Nativism

The “nature” side of the nature-nurture debate: the position emphasising the influence of genetic inheritance and biological maturation over learning and experience, including the view that certain abilities, such as the perception of space, may be innate rather than learned.

Natural selection

Charles Darwin's account of the mechanism driving evolution, in which the individuals best adapted to their environment in a given generation are more likely to survive and reproduce, passing their advantageous traits on to future generations.

Naturalistic observation

The scientific observation of behaviour as it occurs in its natural setting, without any attempt to manipulate or control the situation, as would happen in a formal experiment.

Nature-nurture problem

The long-running question, central to psychology, of the relative contributions of heredity (nature) and environment and experience (nurture) in shaping human psychological characteristics.

Need for achievement

A strongly felt motivation to accomplish goals, meet high standards, and attain success. Some research has linked this motivation to particular patterns of child-rearing, especially early encouragement of independent achievement by mothers, particularly of first-born sons. Associated especially with American psychologist David McClelland.

Need for affiliation

The motivational need to be near and connected with other people, particularly salient when facing a stressful or unpleasant shared experience; situated, in Maslow's hierarchy of needs, above basic physiological and safety needs. Some research suggests this need varies with birth order, with last-born children showing the least need for affiliation and first-born children, especially males, showing the most.

Negative reinforcement

In conditioning, the removal or avoidance of an unpleasant stimulus following a desired response, which strengthens (rather than eliminates) that response — a term often confused, even in professional writing, with punishment, which weakens a response.

Negative transfer

The detrimental effect that previous learning can have on a new learning task, because the two situations require conflicting responses — for example, difficulty steering a boat with a tiller after having learned to steer a car with a wheel. See also: transfer of training.

Neill, A. S. (1883-1976)

A Scottish educator who founded Summerhill School in England with the aim of allowing children to grow up free from unnecessary repression. Though deeply influenced by Freudian ideas, Neill's work has also been embraced by later humanistic psychologists and educators as an expression of their own principles of child-centred learning.

Neo-Freudian

A psychoanalyst who accepts the core framework of Freudian theory while incorporating later modifications and departures from it — Erich Fromm, Karen Horney and Harry Stack Sullivan are prominent examples. Freud's earlier followers who broke away more sharply, notably Alfred Adler and Carl Jung, are usually referred to instead as schismatics rather than neo-Freudians.

Neologism

Literally, a newly coined word. Sometimes found in disordered schizophrenic speech, but far more often encountered in scholarly and scientific writing, either where ordinary words are given new specialised meanings (such as censorship or protocol) or where entirely new terms are invented (such as brainwashing or territoriality).

Neonate

A newborn infant, typically referring to the first four weeks of life.

Nervous breakdown

A popular, non-clinical term for a neurosis or acute psychological crisis severe enough to significantly disrupt a person's ability to function, sometimes requiring hospital treatment.

Nervous prostration

See neurasthenia — an older term for a neurotic state of extreme physical and mental exhaustion.

Nesting instinct

The apparently innate drive in birds to build a nest in preparation for laying eggs. The popular idea that an analogous “nesting instinct” governs human behaviour (for instance, before childbirth) is an example of anthropomorphism, and considerably oversimplifies the complexity of human motivation.

Neuralgia

A disorder affecting a single nerve, producing sharp, localised, intermittent pain along its path.

Neurasthenia

An older diagnostic term for a neurotic condition marked by extreme fatigue, weakness and general debility, both physical and mental, once widely diagnosed but now largely replaced by more specific modern diagnoses.

Neurology

The medical and scientific study of the structure, function and disorders of the nervous system.

Neuron

The basic cellular unit of the nervous system, specialised for receiving, processing and transmitting electrochemical signals.

Neurophysiology

The study of the physiological functioning of the nervous system — how neurons and neural circuits actually operate.

Neuropsychology

The branch of physiological psychology concerned with the relationship between the nervous system, particularly the brain, and mental processes and behaviour, often studied through the effects of brain injury or disease.

Neurosis

A functional psychological disorder, without an identifiable organic cause, whose roots in emotional conflict can often be understood and addressed through psychotherapy. Neurosis may present in various forms, including anxiety, fugue, hysteria, obsession, compulsion or phobia; behaviour suggestive of any of these is described as neurotic.

Night blindness

A significantly weakened capacity for dark adaptation, caused either by an underlying organic disease or by vitamin A deficiency.

Nomothetic

An approach within psychology emphasising the search for general, universal laws or principles governing behaviour, rather than the uniqueness of individual cases. Compare with idiographic.

Non-directive therapy

A therapeutic approach that accepts a client's expression of their own needs and conflicts on their own terms, without imposing a predetermined interpretive framework or steering them toward a particular conclusion. Carl Rogers's client-centred therapy is the most well-known example.

Non-verbal communication

Communication between people through means other than spoken or written language — including facial expression, gesture, eye contact and body posture.

Nonconscious ideology

The largely unquestioned, taken-for-granted assumptions people hold about the world, which can shape their behaviour profoundly even though they remain unaware of holding them.

Nonparametric statistics

Statistical methods that can be applied when data do not meet the assumptions of a normal distribution — a common situation with much real-world data on human behaviour, which often departs from a perfectly symmetrical bell curve.

Nonsense syllables

Meaningless three-letter combinations, such as ZEJ or TUZ, used in memory research because they carry no pre-existing associations that could aid recall (at least to an English speaker).

Norm

In statistics, a value representative of an entire group of scores, such as one of the measures of central tendency (mean, median or mode). See also: group norm, social norm, referring to expected patterns of behaviour rather than a statistical value.

Normal

Literally, conforming to an established norm or standard; as applied to behaviour, it generally refers either to what is statistically typical or expected (the social norm), or to what is considered proper and appropriate given the circumstances.

Normal distribution

The characteristic distribution of data drawn from a random sample of a population, which, when plotted on a graph, forms a symmetrical bell-shaped curve, with most scores clustering near the average and progressively fewer scores toward each extreme.

Normative influence

In social psychology and sociology, the process by which a person's behaviour is shaped by their anticipation of how others will judge it as right or wrong, distinct from informational influence, which is based on others being a source of evidence about reality.

Nuclear family

The immediate family unit of parents and their children, living together as a single household, as distinct from the wider extended family of more distant relatives.

Null hypothesis

In experimental psychology, the default assumption that any observed difference between an experimental group and a control group is simply due to chance, and does not reflect a genuine, significant effect. The purpose of an experiment's statistical analysis is typically to determine whether the evidence is strong enough to reject the null hypothesis in favour of a real effect.

Nystagmus

An involuntary, repetitive jerking movement of the eyes, typically a rapid movement in one direction followed by a slower drift back. It occurs normally for a short time after the head has been spun, but can also be a sign of underlying neurological or brain damage when it occurs without such a trigger.

01 Oct 2026

Glossary of Psychological Terms

Definitions of terms used in psychology, psychometric testing and occupational assessment, organised alphabetically.

MA

An abbreviation for mental age — see that entry.

Machiavellianism

A personality characteristic marked by a willingness to manipulate and exploit others for personal gain, with little regard for conventional morality. Named after the political writings of the fifteenth-century Italian statesman Niccolò Machiavelli, and now also studied as one of the “Dark Triad” personality traits alongside narcissism and psychopathy.

Magic thinking

Any attempt to understand or influence events through recourse to supernatural forces, particularly the belief that one's own wishes can causally affect the real world — “wishing can make it so.” Considered typical of young children, some psychotic states, and pre-literate belief systems, though traces of it are easy to find in ordinary adult behaviour in modern societies as well.

Mandala

In Carl Jung's theory, a circular symbol representing the striving for wholeness and unity of the self, drawing on similar symbols of the cosmos found across many different cultures and religious traditions.

Mania

A state of uncontrollable excitement and elevated energy, often accompanied by a strong impulse toward a particular pattern of behaviour; the elevated phase of bipolar disorder, and also used as a suffix for specific compulsive urges (as in kleptomania).

Manic

Describing behaviour characteristic of mania — marked by excessive energy, elevated mood, and often impulsivity.

Manic-depressive

An older term for the psychotic mood disorder marked by extreme swings between the euphoric excitement of mania and the hopelessness and anxiety of severe depression; the ordinary ups and downs of mood in most people are far milder versions of the same underlying dimension. Now generally referred to clinically as bipolar disorder.

Manifest content

In psychoanalysis, the consciously remembered and reported surface content of a dream, as distinct from its latent content — the hidden, repressed meaning the manifest content is thought to disguise.

Mantra

A word or phrase repeated continuously as an aid to concentration and meditation.

Marasmus

Severe physiological wasting and weakness in infants, resulting from prolonged deprivation of adequate food, care or affection.

Marginality

In social science, the effects on an individual or group of being excluded from, or existing at the edges of, the social and economic mainstream of a society.

Masking

The blocking or obscuring of one sensory stimulus or process by the presence of another, more dominant one.

Maslow, Abraham (1908-1970)

An American personality theorist and leading figure in humanistic psychology, best known for his hierarchy of needs and his concepts of the peak experience and self-actualisation — the realisation of one's fullest personal potential.

Maternal deprivation

The lack of adequate care, affection and attentive handling normally provided by a mother or primary caregiver, particularly damaging during the first few years of life, considered the optimal period for forming secure social attachments. Children who experience severe maternal deprivation, such as those raised in institutional settings, frequently show later physical, psychological or social difficulties. See also: Bowlby, John.

Matriarchy

A society or social group in which women hold the primary positions of authority and leadership. Contrast with patriarchy.

Matrilineal

Describing a society or social group in which lineage, descent or inheritance is traced through the mother's side of the family. Contrast with patrilineal.

Maturation

In psychology, the processes of growth and development common to all members of a species, unfolding on a broadly similar schedule regardless of individual heredity or specific environment — a concept that cuts across, and complicates, the traditional nature-nurture debate.

Maze

An apparatus used to study learning in both animals and humans, ranging from a simple T-junction offering a choice between two paths to an elaborate, multi-branched labyrinth.

McNaughten rules

A mid-nineteenth-century English legal ruling, still influential in many jurisdictions' criminal law, used in determining whether a defendant can be considered legally insane and therefore not criminally responsible. Under the rule, a person is presumed criminally liable unless their reasoning was so impaired that they did not understand the nature of their act, or did not know it was wrong.

Mean

In statistics, the most commonly used measure of central tendency: the arithmetic average, calculated by summing a set of values and dividing by the number of values.

Measures of central tendency

The three main statistics used to describe the central, typical value of a set of numbers: the mean, the median, and the mode.

Median

In statistics, the measure of central tendency that divides an ordered set of scores exactly in half, with as many scores falling above it as below it.

Mediate

In psychology, describing a process, often cognitive, that occurs between a stimulus and the resulting response, helping to explain how the two are connected.

Medical model

The framework that treats psychological disturbance as fundamentally a medical condition, to be diagnosed and treated by physicians, typically with medication. Contrasted with alternative frameworks such as those proposed by the existential psychiatry movement.

Medulla (oblongata)

The lowest part of the brainstem, linking the brain to the spinal cord, which helps regulate essential automatic bodily functions such as blood pressure, heart rate and breathing.

Megalomaniac

A person with a grossly inflated, unrealistic sense of their own importance, abilities or power.

Melancholia

An older clinical term for a pathological degree of low, sorrowful mood, marked by profound sadness and severe depression. See also: involutional melancholia.

Membership group

In social psychology, the group to which a person actually, formally belongs. Compare with reference group, the group whose standards and values a person uses to evaluate themselves, which need not be the same group.

Memory

A term used in three related senses: (1) the cognitive function of encoding, retaining and retrieving information about past experience; (2) the underlying system or systems responsible for storing that information; and (3) the actual content of what is remembered.

Memory span

The number of discrete items a person can accurately recall immediately after a single presentation of the material. See also: digit-span test.

Memory trace

See engram — the hypothesised physical trace a memory leaves in brain tissue.

Mental age

A score derived from an intelligence test, in which test items are graded by difficulty and calibrated against the typical performance of children at each chronological age. See also: intelligence quotient.

Mental defective

An older, now considered outdated and offensive, general term for a person judged to have insufficient mental development to manage ordinary daily life without additional support.

Mental retardation

An older technical term, once standard in Britain and North America, for significant intellectual disability, generally defined as an IQ score below 70; now widely replaced in professional use by “intellectual disability.”

Mental set

A person's expectation of, or readiness for, a particular kind of experience or problem, which can shape (and sometimes bias) how they perceive and respond to a new situation.

Mere exposure

A term introduced by psychologist Robert Zajonc for the finding that, all else being equal, simple repeated exposure to an unfamiliar object, word or image tends to increase how much people like it. Often cited as a partial explanation for the effectiveness of repetitive advertising in shaping consumer preference.

Merrill-Palmer scale

A test of verbal and manual manipulative ability designed for use with young children.

Mesmerism

An early name for hypnosis, derived from the eighteenth-century Austrian physician Franz Mesmer, who developed and popularised the technique under the name “animal magnetism.”

Meta-analysis

A statistical technique for combining and jointly analysing the results of multiple separate studies on the same question, in order to identify overall patterns and trends with greater statistical power than any single study alone.

Metacognition

In cognitive psychology, awareness and understanding of one's own cognitive processes — in effect, thinking about one's own thinking, including monitoring how well one understands or remembers something.

Metapsychology

A term used in two distinct senses: either (1) an ambitious attempt to unify the whole of psychology within a single comprehensive theoretical framework, or (2) speculation that goes beyond existing theory and evidence to address broader questions about the human condition.

Middlescence

A term used within developmental psychology to draw attention to the particular psychological stresses and conflicts of the middle years of adult life, as well as its distinctive and potentially positive aspects.

Milieu therapy

A form of psychotherapy that seeks to help a person by deliberately changing aspects of their surrounding environment, rather than working directly on their individual attitudes or behaviour.

Miller Analogies Test

A test using difficult verbal analogy problems, developed to help predict future academic performance among applicants to graduate programs at American universities.

Mind

A term used loosely for centuries in many different senses; as generally used by psychologists today, it refers to the whole organised system of, primarily cognitive, mental processes — perception, thought, memory and reasoning.

Mind map

A visual note-taking and thinking technique, developed in the 1970s by Tony Buzan, that radiates outward from a central theme using branching lines, shape and colour, intended to support memory, creative thinking and idea generation.

Mind-body problem

One of philosophy's oldest and most persistent questions: how are the mind and the physical body related? Proposed answers have included that mind and body fully interact and influence one another; that they do not interact at all but merely run in parallel; that mind does not really exist as anything distinct from physical brain processes; and that mind and body are, at bottom, one and the same thing.

Minimax strategy

In game theory, a decision strategy that seeks to minimise the maximum possible loss, rather than trying to maximise potential gain — a cautious, risk-averse approach to choosing among alternatives.

Minnesota Multiphasic Personality Inventory

A widely used paper-and-pencil personality test comprising 550 statements that a respondent rates as true or false of themselves. The overall pattern of responses is used to identify personality characteristics, particularly those associated with psychological disturbance, commonly known by its initials, the MMPI.

Mirror writing

Writing produced in reversed form, appearing normal only when viewed in a mirror. Occasionally observed in people diagnosed with schizophrenia, but more commonly seen in young children who have not yet firmly established their hand and directional laterality.

Misanthropic

Describing a disposition of hatred, distrust or contempt for other people in general.

Miscegenation

Technically, interbreeding between genetically distinct population groups; historically used, especially in the context of racial segregation, as a pejorative and scientifically unsound term for relationships or childbearing between people of different racial backgrounds, whose differences are substantially social and cultural rather than biological.

Misogyny

Hatred, contempt or deeply ingrained prejudice against women.

MMPI

An abbreviation for the Minnesota Multiphasic Personality Inventory — see that entry.

Mnemonics

Techniques and tricks used to aid memory, such as acronyms, rhymes, or vivid mental imagery, that make information easier to encode and later retrieve.

Modality

In psychology, a term generally referring to a particular form or channel of sensory experience, such as vision, hearing or touch.

Mode

In statistics, a measure of central tendency referring to the value that occurs most frequently within a set of numbers.

Model

Either (1) a simplified way of representing patterns of relationship observed in human behaviour or mental processes, for research or theoretical purposes; or (2), in social psychology specifically, a person whose behaviour is observed and potentially imitated by others. See also: modelling.

Modelling

In social psychology, a form of learning through observing a model that goes well beyond simple copying or imitation. Children in particular may generalise from a model's specific behaviour to a much wider range of related behaviours of their own devising, rather than reproducing only what they directly observed.

Molar

Describing an activity or behaviour considered as a whole — swimming, for example — rather than broken down into its individual constituent movements. Contrast with molecular.

Molecular

Describing the individual constituent parts of a behaviour — the specific head, arm and leg movements that together make up swimming — rather than the activity considered as a unified whole. Contrast with molar.

Mongolism

See Down's syndrome. This older term, based on a now-discredited and offensive comparison of facial features, is no longer used.

Monogamy

A marriage system involving one husband and one wife for an indefinite period; the prevailing norm in most societies, though far from universal across all cultures and historical periods.

Monozygotic twins

Identical twins, developing from a single fertilised egg (zygote) that splits into two genetically identical embryos. Contrast with dizygotic twins.

Moral development

The area of developmental psychology studying how the capacity for moral judgement and reasoning changes over the lifespan; there is broad, though not universal, agreement that moral reasoning develops through a sequence of stages, as in Lawrence Kohlberg's influential theory, in a manner paralleling other aspects of cognitive development.

Moro reflex

The startle reflex seen in newborn infants, involving a sudden extension and then clutching motion of the arms and legs in response to a sudden loss of support or loud noise, first described by Austrian paediatrician Ernst Moro.

Motion parallax

A depth-perception cue based on relative movement: as an observer moves, nearby objects appear to move faster across the visual field than more distant objects.

Motivation

A general term covering the psychological processes involved in experiencing needs and drives, and the resulting behaviour directed toward goals that satisfy them.

Motor

In psychology, relating to muscular movement and the physical action of the body, as in “motor skills” or “motor cortex.”

Müller-Lyer illusion

A well-known visual illusion in which the perceived length of a line is distorted by the direction of arrow-like fins added to its ends; named after German sociologist and psychologist Franz Müller-Lyer, who first described it.

Multimodal distribution

A frequency distribution containing several distinct modes (peaks), suggesting the data may reflect more than one underlying group or process.

Multiple personality

A rare and dramatic form of dissociative disorder in which repression leads to the apparent splitting off of two or more seemingly complete, distinct personalities within the same individual, as in the fictional cases of Dr Jekyll and Mr Hyde or The Three Faces of Eve. This is what is popularly meant by “split personality,” now more formally termed dissociative identity disorder — not to be confused with the split-brain phenomenon, and never to be confused, as it commonly is in popular usage, with schizophrenia, an entirely distinct condition.

Mundane realism

A term used in social psychology for the degree to which an experimental situation resembles everyday, real-world experience, as distinct from experimental realism, which concerns whether the experiment captures the essential psychological forces of a real situation without needing to replicate its surface details.

Murphy's Law

The informal axiom holding that anything that can go wrong, eventually will — often described as an American or Irish variant of the broader folk principle known as Sod's Law.

01 Oct 2026

Glossary of Psychological Terms

Definitions of terms used in psychology, psychometric testing and occupational assessment, organised alphabetically.

Labelling theory

In social psychology, an account of deviant behaviour that focuses on how other people react to, and label, the person seen as deviant, rather than on the behaviour itself. Combined with the self-fulfilling prophecy, labelling theory has also been used to explain the persistence of psychotic behaviour: once a person is labelled, say, paranoid, everything they subsequently do tends to be interpreted through that lens, reinforcing the original label.

Labile

Describing emotional expression that shifts freely, rapidly and often unpredictably from one state to another.

Laing, Ronald D. (1927-1989)

A Scottish psychiatrist whose sweeping criticisms of conventional psychiatric diagnosis and treatment proved highly influential. A leading figure in the existential psychiatry movement, Laing focused particularly on the roots of emotional disturbance within disturbed patterns of family relationships.

Language codes

See elaborated code and restricted code, Basil Bernstein's two contrasting styles of communication.

Latent content

In psychoanalysis, the hidden, repressed underlying meaning of a dream, as distinct from its manifest content — the dream as consciously remembered and reported.

Latent learning

See incidental learning — learning that occurs without deliberate, conscious effort and may not become apparent until relevant later.

Lateral thinking

A term coined by Edward de Bono for an approach to problem-solving that deliberately looks at a problem from multiple, unconventional angles rather than tackling it head-on, allowing it to be reframed in ways that reveal previously unconsidered solutions. A form of heuristic.

Lateralisation

The process, assumed to occur in brain development, by which each of the two cerebral hemispheres comes to specialise in particular psychological functions, such as language typically lateralising to the left hemisphere.

Laterality

Literally “sidedness”: a person's preference for using one hand, foot or eye over the other for tasks that could be performed with either. See also: bilateral transfer.

Law of parsimony

See Occam's razor — the principle that the simplest adequate explanation for a phenomenon should be preferred over a more complex one.

Laws of association

The principles thought to underlie the connections formed in memory between particular ideas, feelings or behaviours — first systematically formulated by Aristotle in the fourth century BC, and foundational to later associationist theories of learning.

Lay analyst

The term for a psychoanalyst who practises without holding a medical degree, having trained instead through psychoanalytic institutes.

Learned helplessness

The finding that animals or people who have previously experienced a situation in which they could not avoid punishment or an aversive outcome go on to behave passively and give up trying, even later, in situations where they genuinely do have the power to avoid it — an influential concept in understanding depression.

Learning curve

A graph plotting measured changes in learning performance against time or practice, typically showing rapid initial gains that gradually level off.

Learning plateau

A period during which a learning curve flattens out, reflecting a temporary halt in visible progress despite continued practice.

Learning set

Sometimes described as “learning how to learn”: a generalised strategy or approach that a person or animal carries over from one learning situation into a new one, drawing on previously successful responses and strategies. Underlies the broader phenomenon of transfer of training.

Learning styles

The different approaches individuals characteristically take to learning, attributed to individual differences in cognition and personality; though popular, the scientific evidence that matching instruction to a person's preferred “learning style” improves outcomes is weak.

Learning theory

Any of the various systematic attempts within psychology to explain the process and mechanisms of learning, spanning behaviourist, cognitive and social-learning approaches.

Lesion

Damage to bodily tissue caused by injury, disease or surgery; in the study of behaviour, the term is most often used specifically for brain damage, including deliberately induced lesions used in animal research to study brain function.

Level of aspiration

The particular goals or standards of performance a person sets for themselves in a given task or area of life, which may be realistic or unrealistic relative to their actual ability.

Levels of processing

The theory that how deeply information is processed during learning determines how well it is retained in long-term memory: the more meaning a person extracts from and connects to a stimulus, the deeper the processing, and the more likely the information is to be remembered.

Levels of significance

See statistical significance — the threshold probability used to decide whether an observed research result is unlikely to have occurred by chance alone.

Lewin, Kurt (1890-1947)

A psychologist trained under the early Gestalt theorists who applied their principles to social psychology, where he pioneered the study of group dynamics and developed influential concepts including life space and the classic conflict types (approach-approach, approach-avoidance, avoidance-avoidance).

Lie detector

An instrument, more formally called a polygraph, that monitors physiological changes such as heart rate and the skin's electrical resistance under conditions of emotional stress, on the assumption that a person will show detectable signs of emotional arousal if they lie in response to a question — an assumption considered scientifically shaky, with the technique widely regarded as unreliable for reliably detecting deception.

Life instinct

In Freud's theory, an unconscious drive, or set of drives, oriented toward preserving and enhancing life, drawing its energy from the libido. Always contrasted with the death instinct.

Life space

A term introduced by Kurt Lewin for the total combination of physical and psychological factors making up an individual's or group's environment at a given moment, and which together determine their behaviour.

Limbic system

A network of interconnected brain structures thought to play a central role in regulating emotion and motivation, forming part of what is sometimes informally called the “old brain” for its evolutionarily ancient origins.

Limen

See threshold — the minimum level of stimulus intensity needed to produce a detectable sensation or response.

Linguistic determinism

The hypothesis, associated with Benjamin Lee Whorf, that the range of thoughts available to a person is shaped, and potentially limited, by the structure and vocabulary of the language they speak.

Linguistic relativity

See linguistic determinism — sometimes used as a softer version of the same underlying hypothesis, suggesting language influences rather than strictly determines thought.

Little Albert

The infant conditioned by behaviourist John B. Watson, in a famous and now ethically controversial 1920 experiment, to develop a fear response to a white rat by pairing it with a loud, frightening noise.

Little Hans

A young patient of Sigmund Freud's, treated (via the boy's father) for a phobia of horses, and the subject of one of Freud's most detailed published case studies. Not to be confused with Clever Hans, the arithmetic-performing horse.

Lloyd Morgan's Canon

A principle proposed by British comparative psychologist C. Lloyd Morgan in 1894, holding that any interpretation of an animal's behaviour should invoke the simplest possible psychological process capable of explaining it — a higher-level explanation should not be offered when a lower-level one will suffice. A specific application of Occam's razor to animal behaviour.

Lobotomy

A form of psychosurgery in which the connections between the brain's frontal lobes and the rest of the brain are severed. Once used, as a last resort, to treat severe depression and other serious mental illness, the procedure is now rarely performed given its serious and often irreversible side effects, and the availability of far less invasive treatments.

Localisation

In general use, identifying the source or location of a particular stimulus; in psychology, most often encountered specifically as brain localisation, the association of particular psychological functions with particular brain regions.

Locus of control

A personality dimension describing whether a person generally attributes the outcomes in their life to their own actions (an internal locus of control) or to external forces, luck, or other people (an external locus of control).

Long-term memory

The relatively permanent store of memory, capable of holding vast amounts of information over long periods, as distinct from the much more limited and temporary short-term memory and sensory memory.

Longitudinal research

A research design that studies the same group of people repeatedly over an extended period of time, allowing researchers to track change within individuals directly. Compare with cross-sectional research, and see also: cohort effect.

Lorenz, Konrad (1903-1989)

An Austrian pioneer of ethology whose popular books, including King Solomon's Ring and On Aggression, helped bring the scientific study of animal behaviour to a wide general readership; also known for his research on imprinting in young geese.

LTM

An abbreviation for long-term memory — see that entry.

30 Sep 2026

Glossary of Psychological Terms

Definitions of terms used in psychology, psychometric testing and occupational assessment, organised alphabetically.

Kent-Rosanoff test

A word association test consisting of 100 stimulus words, accompanied by a standardised list showing the relative frequency of people's typical responses to each — used to help identify unusual or clinically significant associations.

Kinaesthetic

Relating to the sense that registers the movement and position of the body and limbs, relying on receptors in muscles, tendons and joints. See also: proprioceptors.

Kinsey report

The first large-scale scientific survey of human sexual behaviour, conducted in the United States during the 1940s and 1950s by biologist Alfred Kinsey. Still regarded by some as a groundbreaking and illuminating body of work, despite substantial criticism of its sampling methods and methodology.

Kinship system

In anthropology, the network of family relationships within a society and the behaviours, obligations and roles associated with each type of relationship.

Klein, Melanie (1882-1960)

A pioneering figure in the psychoanalysis of children and in research on depression. Kleinian analysts continue to regard themselves as fundamentally Freudian while diverging from classical Freudian theory on several major points, particularly around early infantile object relations.

Kleptomania

A compulsion to steal, often items of little practical value or need, thought to reflect an underlying psychological disturbance rather than material want. See also: mania.

Köhler, Wolfgang (1887-1967)

One of the founding figures of Gestalt psychology, best known for his research on insight learning in apes, during which he documented the sudden “aha reaction” as chimpanzees solved problems by apparent flashes of understanding rather than trial and error.

Korsakoff's syndrome

A severe memory disorder involving pronounced amnesia, most commonly caused by chronic alcoholism (specifically thiamine deficiency), first described in the nineteenth century by Russian neuropsychiatrist Sergei Korsakoff.

Kuder Preference Record

A questionnaire designed to identify a person's areas of vocational interest, developed by American psychologist G. Frederic Kuder, and an early forerunner of modern career interest inventories.

30 Sep 2026

Glossary of Psychological Terms

Definitions of terms used in psychology, psychometric testing and occupational assessment, organised alphabetically.

J curve

A frequency distribution describing conforming behaviour, in which most people's behaviour clusters at or near what is socially expected, with far fewer people deviating from it — the resulting graph resembles the shape of a capital J, or its mirror image.

James-Lange theory of emotions

A theory combining similar proposals from American philosopher William James and Danish physiologist Carl Lange, holding that emotion is essentially our conscious awareness of bodily changes that follow an arousing event — in this view, we feel sad because we cry, rather than crying because we feel sad. Contrasted with the Cannon-Bard theory, which holds that physiological arousal and emotional experience occur simultaneously and independently rather than one causing the other.

JND

An abbreviation for just noticeable difference — see that entry.

Job analysis

A key task performed by work psychologists, involving systematic study of a job's component tasks and demands in order to match them appropriately with the abilities of the people who perform them.

Jones, Ernest (1879-1958)

A British psychoanalyst and one of Sigmund Freud's earliest and closest followers, who went on to write Freud's official biography.

Jung, Carl Gustav (1875-1961)

A Swiss psychiatrist and one of Freud's earliest close colleagues, at one point considered the likely heir to the psychoanalytic movement Freud founded. Jung broke away in 1914, largely over his rejection of Freud's insistence on sexuality as the central cause of neurosis, and founded his own school, analytical psychology, drawing on interests ranging from mythology and alchemy to Eastern spiritual traditions that Freud's commitment to strict rationalism could not accommodate. See especially: collective unconscious, introversion, extraversion.

Just noticeable difference

The smallest difference between two stimuli that a person can reliably detect — a foundational concept in psychophysics.

Just-world hypothesis

In social psychology, the largely unconscious assumption that the world operates fairly, rewarding the deserving and punishing the undeserving. This belief can lead people to assume that anyone who suffers misfortune must, in some way, have deserved it — a mechanism that helps explain why victims of crime or tragedy are sometimes unfairly blamed for their own circumstances. See also: distributive justice.

30 Sep 2026

Glossary of Psychological Terms

Definitions of terms used in psychology, psychometric testing and occupational assessment, organised alphabetically.

Iconic store

A brief visual memory trace, lasting only a second or two, that preserves an initial impression of a visual stimulus. Compare with echoic store, its auditory equivalent.

Id

From the Latin for “it”: in Freud's structural model of personality, the component housing the deepest, most primitive unconscious drives, closely tied to the body's biological impulses. Governed by the pleasure principle, the id creates problems for the ego whenever its drives are blocked from expression.

Ideal self

The set of values, standards and qualities a person holds for their own self and strives to live up to, whether or not they currently match that ideal.

Idée fixe

French for “fixed idea”: a persistent, obsessive idea or belief that remains unshaken by contradictory evidence or argument.

Identical twins

See monozygotic twins — twins developing from a single fertilised egg, sharing identical genetic material.

Identification

In general use, recognising the identity or nature of someone or something. In psychoanalysis, specifically, the unconscious process of adopting the attitudes, values or behaviours of a person with whom one shares a strong emotional bond, such as a parent.

Identity

The essential, relatively unchanging characteristics that constitute a person's basic sense of unity and continuity as themselves, especially their self-image.

Identity crisis

The acute experience of feeling that one's sense of identity and self have lost their normal stability and continuity, leaving a person disoriented and struggling to recognise or define themselves — a concept central to Erik Erikson's developmental theory.

Identity formation

The central task of the fifth of Erik Erikson's eight psychosocial stages, occurring during adolescence, in which the individual must work out and consolidate their own personal identity.

Idiographic

An approach within psychology that emphasises the uniqueness of the individual case rather than seeking general laws that apply across people. Compare with nomothetic, the search for broad, generalisable principles.

Idiot savant

An older French-derived term, now considered outdated (savant syndrome is the preferred modern term), for a person with an intellectual disability who nonetheless possesses an extraordinary, isolated ability in one specific domain, often music, drawing, memory or calculation — a combination that remains only partially understood.

Illusion

A mistaken perception, arising either from physical causes (as in an optical illusion) or psychological causes (as in a hallucination, though the two are distinguished by whether an external stimulus is actually present).

Imageless thought

A thought, or sequence of thought, occurring with no accompanying mental image or sensory content. Whether such thought genuinely exists has been debated since antiquity; most modern psychologists accept that it does.

Imitation

Copying another person's behaviour, whether as a deliberate, conscious act or an unconscious one. See also: modelling.

Immanent justice

The belief that wrongdoing is inevitably followed by punishment — that even undetected misdeeds will eventually be met with retribution, such as an accident or run of bad luck, imposed by some higher power. According to Piaget, this kind of thinking is typical of egocentric children below around age 8.

Immunisation

See inoculation, in its social-psychological sense of building resistance to persuasion through prior exposure to a weaker version of an opposing argument.

Implicit memory

Memory for previously learned material or skills that a person is not consciously aware of possessing — unlike explicit memory, implicit memory is often substantially preserved in people with amnesia.

Implicit personality theory

The largely unquestioned assumptions people rely on when judging another person's personality — specifically, which traits tend to be assumed to go together. For example, “warm” is commonly assumed to accompany “outgoing,” “sociable” and “good-humoured,” while “cold” is assumed to accompany “withdrawn,” “reserved” and “humourless.”

Impression formation

The process of building an overall judgement of another person by integrating the various pieces of information available about them. See also: impression management.

Impression management

A concept associated with Canadian sociologist Erving Goffman, describing the deliberate effort to present oneself to others in a way calculated to produce a particular, controllable or predictable reaction from them.

Inappropriate affect

An emotional response markedly out of step with the demands of a situation — for example, laughing at a tragic event — often regarded as a symptom of psychosis.

Incidental learning

Learning that occurs without any deliberate, conscious effort — for example, picking up the names of shops passed regularly on the way to a bus stop.

Incremental learning

Learning that proceeds through a series of small, regular, orderly steps, rather than arriving through sudden flashes of insight.

Independent variable

In an experiment, the variable that is deliberately manipulated by the researcher and whose changes form the basis for predicting changes in the dependent variable, rather than depending on any other variable itself. See also: experimental variable.

Individual differences

The systematic comparison of people's characteristics and performance — particularly, historically, intelligence and intelligence test scores, though the field now spans personality, ability and other psychological traits.

Inductive reasoning

A form of reasoning that infers general principles from a set of specific observed cases. Compare with deductive reasoning, which draws specific conclusions from general premises.

Industrial psychology

An older term for what is now generally called work psychology or organisational psychology, still in wide use, particularly in the United States, as “industrial-organisational (I-O) psychology.”

Infantile amnesia

The near-universal inability to recall memories from one's earliest years of childhood. Psychoanalytic theory explains this as a form of repression; other proposed explanations include the absence, at that age, of language sophisticated enough to encode experiences into lasting memory, and the general immaturity of the infant nervous system.

Infantile birth theories

The explanations young children offer, before being told otherwise, for the question “where do babies come from?” — the navel is apparently a particularly popular answer.

Infantilism

A condition in which a person has not psychologically matured beyond an infantile stage of development, or reverts to such a state later in life under stress or disturbance.

Inferential statistics

Statistical procedures that allow researchers to draw generalised conclusions about a larger population based on findings from a smaller, representative sample of that population.

Inferiority complex

A concept from Alfred Adler describing an unconscious condition in which a person feels persistently inadequate and resentful, often centred on some physical characteristic they regard as a defect. The complex can produce distorted behaviour, most notably overcompensation — an exaggerated effort to counteract the perceived defect, sometimes invoked to explain unusually aggressive behaviour in physically small men.

Information processing

A central concept in cognitive psychology describing everything that happens mentally between a stimulus and a response, including perception, memory, thinking, problem-solving and decision-making. “Information,” in this sense, refers broadly to any mental content — an image, idea, fact or opinion.

Information technology

The microelectronic means of transmitting, storing, processing and using information, whether in the form of words, numbers or images.

Information theory

The mathematical study of the nature of information and how it is communicated, originating with mathematicians and engineers (notably Claude Shannon) but subsequently drawn on by psychologists and linguists studying communication and cognition.

Inhibition

The blocking of one physiological or psychological process by another — for instance, activity in one sense receptor suppressing response to another, or fear preventing an escape response. In psychoanalysis, inhibition specifically describes an id impulse being blocked from reaching consciousness by the superego, which is distinct from repression, where the impulse is actively and more forcefully held back.

Inkblot test

See Rorschach test — the well-known projective test using ambiguous inkblot images.

Innate

Describing a genetically inherited tendency or characteristic present from birth, even if it does not become active or apparent until later in life. Compare with congenital, which describes a characteristic present at birth without necessarily being genetically inherited.

Innate releasing mechanism

A concept introduced by ethology pioneer Niko Tinbergen, based on his observations of stickleback fish. Male sticklebacks, who had never seen a female before reaching sexual maturity, still reliably knew to chase off rival males and court females — responding specifically to the presence or absence of red colouring on the belly of the fish they encountered. This specific triggering stimulus is what “releases” the fish's innate behavioural response.

Inner-directed

A term introduced to American sociology by David Riesman for people who respond to social pressures and change primarily on the basis of personal values internalised early in life. Contrast with outer-directed, describing people more responsive to the shifting expectations of their peers.

Inoculation

In social psychology, a technique for strengthening a person's existing attitude, and their resistance to future persuasion, by first exposing them to a small, manageable dose of an opposing argument.

Insight learning

The often sudden appearance of understanding while working through a problem, involving both the discovery of a cognitive solution to a practical difficulty (as in the aha reaction) and the kind of self-understanding sought in psychotherapy. Contrast with trial and error learning, which proceeds through repeated attempts rather than sudden comprehension.

Instinct

An innate, unlearned impulse or behaviour pattern, fixed and largely unchanging, shared by all members of a species; the study of instinctive behaviour in animals falls within ethology. Describing any specific human behaviour as “instinctive” tends to provoke considerable, often politically charged, controversy, and the concept is generally considered of limited value in explaining human behaviour, most of which is learned.

Institutional racism

Racially prejudiced outcomes that arise not from individuals' conscious intent, but simply from conforming to the established norms and conventions of a society whose institutions — law, government, education, business — systematically disadvantage particular racial groups.

Institutionalisation

Used both for the act of committing someone to an institution, such as a psychiatric hospital, and for the resulting state of a long-term resident who has adapted so completely to institutional life that they become unable to function independently outside it.

Instrumental aggression

A term from social psychology for aggression carried out not for its own sake, but as a means to achieve some other goal — illustrated by the psychological difference between killing an enemy face-to-face and remotely launching a missile from a great distance.

Instrumental conditioning

See operant conditioning — an alternative name emphasising that the organism's behaviour is “instrumental” in producing its consequences.

Integration

The process of organising separate parts into a coherent whole of a higher order — a concept applied across science, from the coordination of nerve impulses underlying any behaviour to the organisation of an entire society.

Intellectualising

Approaching a situation in purely intellectual, abstract terms while ignoring or denying the emotional content involved; regarded in psychoanalysis as a defence mechanism that protects the ego from uncomfortable feelings.

Intelligence

A concept psychologists have debated since the 1870s without reaching full agreement on its definition. Most would agree that heredity sets some limits on a person's intelligence, and that the capacity to learn — handling abstract ideas, adapting to new situations, perceiving complex relationships — is a marker of high intelligence, though this offers only a loose working definition. Intelligence is often cited as a clear example of a phenotype, the observable outcome of both genetic potential and environmental influence.

Intelligence quotient

A score derived from an intelligence test by dividing a person's mental age (as measured by the test) by their actual chronological age and multiplying by 100 (IQ = MA/CA × 100). An IQ score on its own has no absolute meaning — it does not measure intelligence the way a tape measure measures height — but only reflects a comparison against everyone else who has taken that particular test, with the average score conventionally set at 100.

Intelligence test

A test intended to measure intelligence, used to distinguish higher- and lower-scoring individuals for educational, occupational or social purposes. In the absence of a fully agreed definition of intelligence itself, the practical, or operational, definition risks circularity — people are said to score well because they are intelligent, and to be intelligent because they score well. There is also considerable evidence that intelligence tests have historically been biased in favour of white, urban, middle-class test-takers in the design and selection of their items.

Interaction process analysis

A technique for systematically recording and analysing the patterns of interaction between people within a face-to-face group.

Interaction recorder

A device used to time and record different categories of interaction occurring within face-to-face groups, for research purposes.

Intercorrelations

A table displaying the correlations calculated between every possible pair within a set of variables, used especially in factor analysis.

Interference

A term with two main psychological meanings: (1) the change in perception that occurs when two light or sound waves, out of phase with one another, combine; and, more commonly, (2) the process by which one instance of learning disrupts or inhibits another, as studied in memory research.

Intermittent reinforcement

In a conditioning experiment, rewarding an animal for correct responses only some of the time, rather than every time. This tends to produce conditioning that is slower to establish but considerably more resistant to extinction than continuous reinforcement.

Internal justification

In social psychology, a way of resolving cognitive dissonance that underlies particularly durable attitude change: rather than justifying an uncomfortable choice with an external reason (“I only do it for the money”), a person instead comes to genuinely see the situation more positively — for example, focusing on an unappealing job's more rewarding aspects — thereby changing the underlying attitude itself.

Internalisation

The process of accepting external ideas, values or standards as one's own, to the point where their original outside source is no longer consciously recognised. Its best-known example is the superego, in which the values of parents and wider society become built into the developing personality.

Interpersonal attraction

A general term for the area of social psychology concerned with understanding why people are drawn to one another. See also: gain-loss theory of interpersonal attraction.

Interposition

A depth cue in which one object partially blocks another from view, providing information that the blocking object is nearer to the observer.

Intervening variable

A hypothetical process or variable assumed to occur between a stimulus and a response, inferred rather than directly observed. See also: black box.

Intrapsychic

Describing conflicts or processes occurring entirely within the psyche — that is, within the mind, personality or self — as distinct from conflicts between a person and their external environment.

Intrinsic motivation

Doing something for its own sake, because the activity itself is rewarding, rather than for any external reward or consequence. Always contrasted with extrinsic motivation. See also: functional autonomy.

Intropunitive

Characteristically responding to frustration by blaming, punishing or feeling guilt and humiliation toward oneself. Contrast with extrapunitive, in which frustration is directed outward at others.

Introspection

The deliberate process of examining and reporting on the contents of one's own mind — one of psychology's earliest research methods, associated particularly with Wilhelm Wundt's early laboratory studies.

Introversion

In Carl Jung's theory, a fundamental personality dimension characterised by a withdrawn, inward-looking and relatively passive orientation. Usually contrasted with extraversion.

Involution

Literally the opposite of evolution — decline or deterioration, used particularly to describe the physical and psychological changes and crises associated with midlife. See also: involutional melancholia, middlescence.

Involutional melancholia

A state of depression and anxiety traditionally associated with menopause and with midlife crises more generally; the term is now largely superseded in clinical use by more specific modern depressive diagnoses.

IQ

An abbreviation for intelligence quotient — see that entry.

IRM

An abbreviation for innate releasing mechanism — see that entry.

Irrational

Describing thought or behaviour that is inconsistent with logic or reason.

Ishihara test

A widely used test for colour blindness in which a person is asked to identify a number or pattern embedded within a background of dots in different, carefully chosen colours; people with normal colour vision can perceive the pattern clearly, while people with colour blindness generally cannot.

Isomorphic

An idea, revived by Gestalt psychology, proposing a direct, one-to-one correspondence between a perceived stimulus and its representation in the brain. The concept has now largely been abandoned in mainstream neuroscience and cognitive psychology.

IT

An abbreviation for information technology — see that entry.

Item analysis

A statistical technique used to evaluate how effectively individual items on a test discriminate between higher- and lower-scoring test-takers, informing the refinement of psychometric instruments.

30 Sep 2026

Glossary of Psychological Terms

Definitions of terms used in psychology, psychometric testing and occupational assessment, organised alphabetically.

Habit

A learned response to a given situation, performed so regularly that it appears virtually automatic — closely enough resembling innate behaviour that habits are sometimes mistakenly regarded as instincts.

Hallucinogen

A drug, such as LSD or mescaline, capable of inducing hallucinations — perceptual experiences with no corresponding external stimulus.

Hawthorne effect

The finding that simply paying attention to workers improves their performance, first identified in studies at the Hawthorne Works of the Western Electric Company in Illinois during the 1920s. Researchers varied conditions such as lighting, rest breaks, working hours and pay systems; each change increased productivity — as, eventually, did reverting to the original conditions. The investigators concluded that it was not the specific environmental changes that mattered, but workers' perception that management was taking an interest in them and their work — a striking example of social facilitation.

Hebephrenia

An older term for a form of schizophrenia characterised by giggling, silliness, and displays of emotion inappropriate to the situation; now generally subsumed under broader schizophrenia diagnostic categories.

Heredity

The biological transmission of physical and, to a debated degree, psychological characteristics from parents to their offspring via genes.

Heuristic

Originally, a method or idea in teaching that stimulates further thinking and discovery; now used more broadly for any mental rule of thumb or shortcut that helps a person make a decision or solve a problem quickly, often at some cost to accuracy.

Higher mental processes

A general term for thinking — including learning, memory, reasoning and imagination — as distinct from more basic sensory processes.

Horopter

In binocular vision, when both eyes are fixed on the same point, the horopter is the set of all points in space whose images fall on corresponding locations on both retinas, and which are therefore perceived as a single, fused image rather than as double vision.

Human communication

The exchange of information between people by any means — verbal, through speech and writing, or non-verbal, through gesture, expression and tone. The study of the field draws on psychology, social science, linguistics, computer science and logic.

Human engineering

See ergonomics — the study of the interaction between people and the tools, machines and environments they work with.

Human factors

See ergonomics.

Human performance factors

The American term for ergonomics.

Humanistic psychology

A school of psychology emphasising the qualities that distinguish human beings from other animals — creativity, humour, play and psychological growth. Sometimes called the “third force” in psychology, positioned as an alternative to both behaviourism and psychoanalysis. Its leading figures include Gordon Allport, Abraham Maslow and Carl Rogers.

Huntington's chorea

Also called Huntington's disease: a hereditary, progressive neurodegenerative disorder affecting muscle coordination and leading to cognitive decline and dementia, typically becoming apparent in middle age. It is the most common genetic cause of chorea — involuntary, writhing movements — and occurs considerably more often in people of Western European descent than in those of Asian or African descent.

Hydrocephalus

A condition involving an excessive build-up of cerebrospinal fluid within the skull, resulting in an enlarged skull and, without treatment, underdeveloped brain tissue.

Hydrophobia

Literally, “fear of water”: the medical term for a symptom of rabies in humans, in which attempting to swallow triggers throat spasms. Despite the name, the fear involved is a direct physiological symptom of the disease, not a psychologically abnormal phobia.

Hyperthyroidism

A condition of excessive hormone secretion by the thyroid gland, which can produce heightened physical activity, restlessness and emotional excitability.

Hypnagogic images

Vivid, often hallucinatory images and sensations experienced during the transitional period of falling asleep.

Hypnogenic

Describing anything that helps induce a state of hypnosis.

Hypnosis

An induced state of heightened suggestibility to a hypnotist's instructions. Though the typical hypnotic trance outwardly resembles sleep, EEG recordings show it is a distinct physiological state. Despite centuries of interest, the underlying mechanism of hypnosis remains poorly understood, though it is a clearly real and, in the right circumstances, powerful phenomenon — as far back as the mid-nineteenth century, surgeons James Braid and James Esdaile reportedly performed battlefield surgery using hypnosis as the sole anaesthetic, a practice that ended with the introduction of chloroform.

Hypnotherapy

The therapeutic use of hypnosis within psychotherapy, for purposes such as pain management, habit change or accessing suppressed memories.

Hypochondria

A neurotic, excessive preoccupation or worry about having a serious illness, often persisting even after a physician has thoroughly evaluated a person and found no underlying medical cause — or, where illness is present, worrying far beyond what the actual severity warrants. Many people with hypochondria fixate on a particular set of symptoms, such as gastrointestinal complaints, heart palpitations or muscle fatigue, as the focus of their anxiety.

Hypothalamus

A small but critical region at the base of the brain responsible for regulating many basic bodily processes, including temperature, hunger, thirst and the release of hormones via the pituitary gland.

Hypothesis

A proposed explanation for an observed pattern of data, put forward in a form that can be tested through further observation or experiment.

Hypothetical construct

A theoretical concept, invented by a researcher or theorist to make sense of an observed phenomenon, without necessarily being directly observable itself — an ordinary and essential part of scientific progress, applying as much to a physicist's “atom” as to a psychologist's “personality.”

Hysteria

From the Greek word for “womb,” reflecting the historically mistaken belief that the emotional disturbances it describes were exclusively female and caused by disorders of the uterus. There is no full consensus on hysteria's defining symptoms, though most authorities treat dissociation as a central feature; conversion hysteria is its most striking recognised form. Psychoanalysis treats all hysteria as a form of neurosis arising from unconscious conflict. See also: battle fatigue, sometimes described as a male-presenting form of hysteria.

Hysterical paralysis

See conversion hysteria — the loss of motor function in a limb or body part with no identifiable physical cause, understood as a physical expression of underlying psychological conflict.

30 Sep 2026

Glossary of Psychological Terms

Definitions of terms used in psychology, psychometric testing and occupational assessment, organised alphabetically.

Gain-loss theory of interpersonal attraction

A theory of liking proposing that changes in the rewarding behaviour we receive from another person affect us more strongly than a consistently steady level of that behaviour. As a result, people tend to feel most positively toward someone who starts out unfavourable and becomes more positive, and least favourably toward someone who starts out positive and becomes negative.

Galton, Francis (1822-1911)

A British scientist, cousin and disciple of Charles Darwin, who pioneered the systematic measurement of individual differences in mental ability, laying groundwork for psychometrics and the study of intelligence, though his later advocacy of eugenics is now regarded as a deeply problematic part of his legacy.

Gallup poll

The first, and still best-known, technique for scientifically sampling public opinion on a large scale, invented by American statistician George Gallup in the 1930s.

Galvanic skin response

A measurable change in the skin's electrical conductivity, detected through electrodes on the skin's surface, that occurs during states of emotional arousal. The correlation between this response and emotional state forms the basis of the polygraph, or “lie detector” test — though, as with any correlation, exactly what a given reading means remains open to interpretation.

Game theory

A mathematical approach to studying conflict and decision-making that models conflict situations as games with defined strategies and rational players. Simpler scenarios studied under this framework, such as the Prisoner's Dilemma, have proven useful to social psychologists as models for generating ideas about real social behaviour.

Gatekeeping

In sociology, the process by which certain people are selected into, or excluded from, a society's elite circles or positions of influence.

Gaussian curve

The bell-shaped curve describing a normal distribution, named after the nineteenth-century German mathematician Carl Friedrich Gauss.

Gender identity

A person's sense of belonging to, or identifying as, male, female, or another gender identity, as distinct from biological sex assigned at birth.

Gene

The basic unit of heredity: a segment of DNA within a cell that carries information determining an inherited characteristic.

Generalisation

The process of forming a judgement about an entire category based on experience with only a limited sample of it — a basic principle underlying both scientific reasoning and everyday learning, though one prone to error when the sample is unrepresentative.

Generalised other

A concept from American sociologist George Herbert Mead for a person's internalised sense of how other people, in general, expect them to behave in a given situation. Compare with significant other, referring to a specific individual whose expectations particularly matter to a person.

Generation gap

Differences in attitudes, beliefs and values between parents and children, attributed at least partly to being socialised during different historical periods. Though generation gaps have likely existed throughout history — suggesting the underlying pattern is real — the size of the gap in any given era may be more apparent than substantive. See also: cohort effect, socialisation, zeitgeist.

Generativity

The central task of the seventh of Erik Erikson's eight psychosocial stages, typically arising in middle adulthood, involving the capacity for creative or productive work, mentorship, or parenting that contributes to future generations.

Genetics

The scientific study of heredity — how traits are passed from parents to offspring through genes.

Genital stage

In Freud's theory of psychosexual development, the final, mature stage in which a person becomes capable of a loving, fully realised sexual relationship, achieved only if earlier stages of development have been successfully navigated without becoming fixated.

Genotype

An individual's full genetically inherited potential, as distinct from the phenotype — the traits that are actually expressed, which result from the interaction between genotype and environment.

Gerontology

The scientific study of old age and the biological, psychological and social processes of ageing.

Gesell development norms

A pioneering set of developmental milestones, produced by American psychologist Arnold Gesell, charting the typical timetable at which physical and motor abilities emerge in infants and young children.

Gestalt completion test

A test using incomplete pictures that can be identified correctly only if the viewer perceives the underlying overall pattern, or gestalt, of the image rather than its individual disconnected parts.

Gestalt psychology

A school of psychology that emerged in the early twentieth century, largely in reaction to the behaviourism of Pavlov and Watson, holding that psychological phenomena must be understood as unified wholes (gestalten) that cannot be reduced to their individual component parts. Its founders, Kurt Koffka, Wolfgang Köhler and Max Wertheimer, developed the approach chiefly through studies of perception — noting how the brain organises individual dots of light into coherent visual patterns, or separate notes into a melody. Köhler later extended the approach to insight learning in apes (see: aha reaction), and later Gestalt-influenced psychologists such as Kurt Lewin and Kurt Goldstein applied its principles to personality and social psychology. Gestalt insights into perception are now broadly accepted within mainstream psychology and align closely with the cognitive revolution, though some argue certain aspects of behaviour are still best explained by analysing their component elements.

Gestures

Bodily movements, particularly of the hands and face, used for the purpose of communication, whether consciously intended or not.

Glossolalia

“Speaking in tongues”: fluent vocalisation that resembles an unknown language but is not one, most commonly associated with states of religious ecstasy, though also observed in people experiencing severe emotional disturbance.

Goal-directed behaviour

Animal or human behaviour that can only be adequately understood by assuming it is organised around, and intended to achieve, a specific goal, rather than being a simple mechanical response to stimuli.

Goodenough Draw-a-Person Test

An intelligence test for children under 12, developed by American psychologist Florence Goodenough, in which the child is asked to draw a picture of a person; scored for detail and accuracy, it is considered relatively, though not entirely, free of cultural bias compared with many other intelligence measures.

Gradient

A constant, measurable rate of change between two conditions or variables, used across psychology wherever a quantity changes systematically — for instance, a gradient of similarity, or a stimulus gradient in learning theory.

Grand mal

See epilepsy — the severe form of epileptic seizure involving violent convulsions and prolonged loss of consciousness.

Graphology

The analysis of a person's handwriting as a projective technique, on the theory that handwriting style reveals aspects of personality; its scientific validity is not well supported by empirical research.

Grasping reflex

The automatic closing response of the fingers or toes when the palm or sole is touched; present from birth and studied as one of several primitive infant reflexes.

Great-man theory

The historical theory that the course of events is shaped, at crucial turning points, primarily by the decisive actions of a small number of extraordinary individuals — now generally regarded, as an explanation of history, as a considerable oversimplification that neglects broader social, economic and structural forces.

Group norm

The pattern of behaviour expected of every member of a particular group; see also: norm.

Group polarisation

The tendency for group discussion to push individual opinions and decisions toward a more extreme version of the position members already leaned toward beforehand — in either a riskier direction (risky shift) or a more cautious one (cautious shift). Known in American usage as choice shift.

Group test

A test, typically a paper-and-pencil test, administered simultaneously to a large group of people rather than one individual at a time.

Group therapy

Psychotherapy conducted with several people simultaneously, based on the premise that participants can benefit not only from the therapist's guidance but from the shared experience, feedback and companionship of the other group members.

Grouping

The statistical process of combining individual scores into categories, or ranking them relative to one another — for example, sorting scores into percentiles.

Groupthink

A term coined by psychologist Irving Janis in the early 1970s for the tendency of members of a highly cohesive group to become so focused on preserving consensus and unity that their critical, independent judgement becomes dulled, sometimes leading the group toward poor or even disastrous decisions.

Guilt

The awareness of having violated a social norm of behaviour one personally identifies with, accompanied by a feeling of regret. In psychoanalytic theory, guilt arises from unconscious conflict in which the superego dominates, and can produce neurotic symptoms if the underlying conflict is never resolved.

30 Sep 2026

Glossary of Psychological Terms

Definitions of terms used in psychology, psychometric testing and occupational assessment, organised alphabetically.

F-Scale

A questionnaire developed during the classic study of the “authoritarian personality” to measure a person's tendency toward authoritarianism (the F stands for fascism). Based on clinical work and social surveys, its designers held that someone prone to authoritarian, rigidly conventional attitudes and preoccupied with power and submission to authority would score high, while a more open, flexible person would score low. See also: California F Scale.

Fabulation

The telling of fantastic, invented stories as though they were true, done knowingly rather than involuntarily — distinct from confabulation, in which someone with a genuine memory disturbance believes their invented account to be accurate.

Face recognition

The study of the perceptual and cognitive processes involved in recognising faces — an increasingly prominent area of research within both cognition and perception, with applications ranging from clinical neuropsychology to security technology.

Face validity

The extent to which a psychological test or measurement procedure appears, on its face, to be relevant to what it claims to measure — a relatively weak form of validity compared with construct or predictive validity.

Face-to-face group

A social-psychological term for a small group of people in close enough physical proximity that each person can interact directly with every other member; such groups are generally limited to around six to eight people.

Facework

In social psychology, the social rituals and behaviours people use to preserve or enhance their public image (“save face”), sometimes at the expense of expressing genuine emotion.

Facilitation

A general term meaning to make something easier, applied either to the performance of a behaviour or to the transmission of a nerve impulse. See also: social facilitation, the specific effect of an audience or co-actors on performance.

Factor analysis

A statistical technique for analysing complex patterns of correlation among a large set of scores, in order to identify a smaller number of underlying factors that account for those correlations — widely used in the development of personality and intelligence tests.

Faith healing

An attempt to cure illness through non-rational belief rather than medical treatment, most often religious in nature. There is some evidence that faith healing can influence psychosomatic illness, where psychological factors play a significant role, but far less support for any effect on purely organic disease.

False memory syndrome

The experience of having a vivid, sincerely held memory of an event that did not actually happen, sometimes arising through suggestion, particularly in therapeutic or investigative contexts; a topic of considerable controversy in memory research and the legal system.

Family therapy

A form of psychotherapy in which the family, rather than a single individual, is treated as the unit of concern, based on the premise that an individual's apparent neurosis may actually be a symptom of disturbed relationships within the family system.

Fantasy

A deliberate exercise of the imagination, typically to enjoy pleasurable, wish-fulfilling images, though fantasy induced by drugs or occurring involuntarily can also be distressing rather than pleasant.

Father figure

A person perceived as standing in for one's actual father, becoming the object of emotions originally directed at him; more broadly, an older person, usually in a position of authority, with whom one identifies and from whom one seeks approval and guidance.

Fear of failure

An anxiety aroused when a person feels pressure to succeed, particularly prevalent among people with a strong underlying need for achievement.

Fear of success

A motive, first studied mainly in women, to avoid excelling or succeeding — particularly in competition with men — because socialisation has led the person to see such achievement as violating expected gender roles; now recognised as relevant to men as well, and sometimes difficult to distinguish from fear of failure.

Fechner's law

Named for German physicist and psychologist Gustav Fechner: the principle that as the physical intensity of a stimulus increases, the intensity a person perceives increases only proportionally more slowly, expressed mathematically as S = k log R (perceived intensity as a logarithmic function of physical intensity). One of the earliest attempts to express a psychological phenomenon mathematically, it emerged from the psychophysics research that helped establish psychology as an experimental science in the 1870s.

Feedback

A concept borrowed from cybernetics, describing the relationship between a system's output and its input, where information about output is fed back to regulate future input. Widely applied in programmed learning and teaching-machine design, and more generally in any process where knowledge of results shapes subsequent performance.

Feeling tone

The overall pleasantness or unpleasantness of the sensation produced by a given person, object or situation.

Feminism

A social movement and set of viewpoints committed to eliminating prejudice and unequal treatment based on sex, and to advancing women's interests and equality more broadly.

Feral child

A child said to have been raised by animals in the wild, largely isolated from human contact. Such accounts are part of popular psychology folklore and are generally regarded with considerable scepticism by researchers.

Field

In psychology, a term sometimes used for the whole set of interdependent factors within an organism's environment that together give rise to a particular piece of behaviour, drawing on an analogy with the physical concept of a field of force.

Field dependence-independence

The idea that people rely on one of two distinct cognitive styles, tied to distinct personality patterns, when orienting themselves within their environment (or “field”): field-independent people rely less on surrounding visual cues, while field-dependent people rely on them more heavily for orientation and judgement.

Field work

Any study of human or animal behaviour carried out outside a laboratory or formal experimental setting, in the subject's natural environment.

Fight-or-flight reaction

Originally a zoological term for the built-in behavioural choices an animal has when confronted by an intruder into its territory; extended to describe the human physiological and behavioural response to perceived threat, though the human version is considerably more complex than the phrase's common, oversimplified use suggests. Inability to either fight or flee in the face of a threat is considered a frequent trigger for stress.

Figural after-effect

A perceptual distortion in which viewing a second pattern after a different first pattern causes the same figure-ground relationships seen in the first to be perceived, at least partially, in the second.

Figure-and-ground

A principle holding that perception requires the perceptual field to be organised into a figure, distinguished against a relatively uniform background (ground). The figure is usually the element receiving attention, though figure and ground can reverse, as vividly illustrated by ambiguous figures such as reversible-image illusions.

Fixed action pattern

A more contemporary ethological term for what was traditionally called instinct — a largely innate, stereotyped behavioural sequence triggered by a specific stimulus.

Fixed-alternative

Describing a test or questionnaire item that requires a respondent to choose an answer from a fixed set of given alternatives, as opposed to an open-ended response.

Flattening of affect

A notable weakness or absence of emotional expression in situations where a stronger emotional response would ordinarily be expected; a clinical sign often associated with schizophrenia and certain other conditions.

Flicker fusion frequency

See critical flicker frequency — the point at which a flickering light is perceived as steady.

Flight into illness

A term from clinical psychology for developing symptoms of illness as an unconscious way of escaping an underlying conflict; some social scientists have proposed this as a significant contributing factor in mental illness among people facing severe socioeconomic disadvantage.

Folie à deux

French for “insanity of two”: a delusion shared by two people, typically a couple or close pair who live together and reinforce each other's mistaken belief.

Forced-choice technique

A testing method in which a respondent must select one option from a fixed set of alternatives, even if none of the options feels fully accurate or appropriate to their own view.

Forensic psychology

The application of psychological research and theory to legal issues, including criminal behaviour, jury decision-making, and the reliability of eyewitness testimony.

Formal operations

The fourth and final stage in Jean Piaget's theory of cognitive development, spanning roughly ages 12 to 16, during which a person becomes capable of abstract reasoning, hypothetical thinking and formal logical deduction.

Fraternal twins

See dizygotic twins — twins developing from two separately fertilised eggs, genetically no more alike than ordinary siblings.

Free association

A core technique Freud developed for psychoanalysis, in which the patient is asked to voice whatever thoughts and images come to mind, following their own train of thought without guidance or censorship from the analyst. Over time, patterns within these associations can reveal underlying areas of unconscious conflict.

Free-floating anxiety

A chronic state of anxiety that cannot be traced to any specific source, and which can attach itself, seemingly arbitrarily, to almost any object, thought or situation.

Frequency

Either the number of cycles per second of a light or sound wave (relevant to phenomena such as pitch and colour perception), or, in statistics, the number of times a particular value or event occurs within a data set.

Frequency distribution

A statistical tabulation showing how often each value, or range of values, occurs within a data set, often displayed as a table or graph.

Freud, Sigmund (1856-1939)

The founder of psychoanalysis, whose work spans a therapeutic technique, a theory of personality, and a broader social philosophy. Freud's ideas developed partly out of his own self-analysis, notably his troubled reaction to his father's death, which led him toward his unconscious ambivalence about his father and about his own Jewish identity — material that shaped The Interpretation of Dreams, widely regarded as his most original and influential book. Drawing on his own experience and clinical work with patients, he developed a theory of personality centred on the formative importance of early childhood in shaping the ego, superego and id and their ongoing interplay in adult life. In later works, including Totem and Taboo, The Future of an Illusion and Civilization and Its Discontents, he extended his thinking to society at large, arguing that repression, and the resulting neurosis, is an inevitable cost of civilised life. While individual elements of Freud's theory remain hotly contested by both Freudians and critics, his broader influence in bringing unconscious and irrational forces into mainstream understanding of human behaviour is widely acknowledged.

Freudian slip

A slip of the tongue that Freud, who held that nothing in human behaviour is truly random or accidental, interpreted as a meaningful clue revealing a repressed unconscious conflict. See also: parapraxis, the broader category of such unintentional errors.

Frustration-aggression hypothesis

The proposition that frustration reliably leads to aggression in both animals and humans, and that aggression is always preceded by some frustration. Subsequent research has identified enough exceptions to both halves of this claim that the exceptions are now considered at least as theoretically important as the general pattern.

Fugue

From the Latin for “flight”: an extended period of amnesia during which a person leaves home, forgets their past, and begins a new, often quite different, life elsewhere. Once the underlying unconscious conflict driving the amnesia is resolved, the person typically recovers their original memory and identity, and in turn forgets the fugue period itself.

Functional autonomy

A concept from Gordon Allport describing how a behaviour originally performed to reach some external goal can become rewarding, and pursued, for its own sake — relevant to how extrinsic motivation can, over time, become genuinely intrinsic. For example, a child who initially practises an instrument only to satisfy parental demands may come to enjoy playing purely for its own sake.

Functional disorder

An emotional or behavioural disturbance that cannot be attributed to any identifiable physical or organic cause. As a rough rule of thumb, such disturbances have traditionally been classed as neuroses, with organically caused disorders classed as psychoses — though this is a considerable oversimplification of a complex and still incompletely understood distinction.

Functionalism

A school of psychology emphasising the functions or purposes of mental activity — what the mind does and why — rather than its content or structure, which was the focus of its historical rival, structuralism.

Fundamental attribution error

The pervasive tendency, when explaining someone else's behaviour, to overestimate the influence of their personal characteristics (disposition) and underestimate the influence of their situation or social environment.