Definitions of terms used in psychology, psychometric testing and occupational assessment, organised alphabetically.
Zero-sum game
In game theory, a situation in which one participant's losses are exactly balanced by another's gains, because the total amount available to be won is fixed — the gains and losses across all players sum to zero. Sometimes proposed, controversially, as a model for how rewards are distributed within society more broadly.
Zoomorphism
The interpretation or description of human behaviour using concepts and terms properly applicable to animal behaviour — the reverse of anthropomorphism, which projects human qualities onto animals.
Zygote
In humans and other higher animals, the single cell formed by the union of a sperm cell and an egg cell at fertilisation, from which, through subsequent cell division, a new individual organism develops.
Definitions of terms used in psychology, psychometric testing and occupational assessment, organised alphabetically.
X and Y chromosomes
The chromosomes that determine biological sex. In most species, including humans, females typically carry two X chromosomes, while males carry one X and one Y chromosome.
Definitions of terms used in psychology, psychometric testing and occupational assessment, organised alphabetically.
Whole method
A technique for learning material in which the entire body of content is studied as a single unit on each practice repetition, rather than being broken into sections. Compare with part method.
Word association test
A technique for probing areas of psychological difficulty a person may have repressed. The respondent is asked to give an immediate response to each word in a pre-selected list, with both their answers and their reaction time to each word carefully noted and analysed.
Work psychology
The branch of psychology concerned with the world of work, encompassing personnel selection, training, job satisfaction, the physical and social work environment, organisational structure, workplace relationships, and ergonomics.
Wundt, Wilhelm (1832-1920)
A German physician and philosopher widely regarded as the founder of experimental psychology as a distinct scientific discipline. In 1879, Wundt established the first formal laboratory dedicated to psychological research, at the University of Leipzig, where he and his students used introspection and controlled experimental methods to study sensation, perception and reaction time. His influence extended across a generation of early psychologists trained in his laboratory, many of whom went on to found psychology programs across Europe and the United States.
Definitions of terms used in psychology, psychometric testing and occupational assessment, organised alphabetically.
Validity
In logic, validity refers to whether an argument's conclusion follows correctly from its premises, regardless of whether the premises themselves are actually true. In psychological testing specifically, validity refers to whether a test genuinely measures what it claims to measure. See also: construct validity.
Variable
A condition, factor or quantity, typically within an experiment, that is capable of taking different values — whether it changes naturally or is deliberately changed by the researcher. See also: independent variable, dependent variable.
Variance
In statistics, a measure of the spread or dispersion of a set of scores around their mean, calculated as the average of the squared deviations from the mean, and equal to the square of the standard deviation.
Vygotsky test
A test of concept-formation ability requiring a person to sort a series of blocks by colour, shape and size; named after Lev Vygotsky, a leading Russian psychologist and pioneer in studying the relationship between thought, language and intellectual development.
Visual dominance
The tendency, when a person receives conflicting information from different sensory modalities simultaneously, for vision to take precedence over the other senses in shaping perception and judgement.
Definitions of terms used in psychology, psychometric testing and occupational assessment, organised alphabetically.
Unconditioned stimulus
A stimulus that reliably produces an unconditioned response from the very start of a conditioning procedure, before any learned association has been established — for example, food producing salivation.
Unconscious
The most important concept within dynamic psychology, and psychoanalysis in particular: the region of the psyche holding impulses and desires too threatening to be allowed into consciousness, and which have therefore been repressed or otherwise kept from entering it. The effects of this repression are expressed, in consciousness, as neurotic behaviour. Freud did not discover the unconscious, and never claimed to have done so, but he did more than anyone to systematically probe its dynamic relationship with the conscious mind, and to expose the considerable degree of irrationality underlying human affairs.
Unconscious motivation
Motivation for a thought, feeling or action that originates outside a person's conscious awareness, so that the person may sincerely believe their behaviour is driven by entirely different, consciously acknowledged reasons — a foundational assumption of psychoanalytic theory.
Underachiever
A person who fails to reach the level of achievement expected of them given their apparent ability. Sometimes used in education to describe someone judged not to be trying hard enough relative to their potential. Contrast with overachiever.
Undoing
In psychoanalysis, a defence mechanism in which a person performs some, often ritualised, act in the unconscious hope of magically reversing or cancelling out an earlier act that continues to disturb them. Considered the underlying mechanism behind obsessive-compulsive neurosis, the classic literary example being Lady Macbeth's guilt-driven hand-washing.
Utilitarianism
The philosophical position holding that the practical usefulness of an idea, action or policy is the sole legitimate criterion of its value — an approach that, applied uncritically to the study of human behaviour, has at times constrained deeper understanding by favouring what appears immediately useful over what is actually true.
Definitions of terms used in psychology, psychometric testing and occupational assessment, organised alphabetically.
T maze
The simplest form of maze, shaped like the letter T, presenting an animal with a single choice between two paths.
T-group
A form of sensitivity training, conducted in small groups focused on developing self-awareness and interpersonal skills through open discussion of feelings and group process.
T-test
In statistics, a test used to determine whether the means of two groups of scores differ from each other by more than would be expected by chance alone.
Task leader
The person who tends to emerge within a small group as the one who keeps the group focused on its task and ensures the work actually gets done. Compare with socio-emotional leader, who instead focuses on maintaining group morale and relationships.
TAT
An abbreviation for the Thematic Apperception Test — see that entry.
Teaching machine
A mechanical or electronic device designed to support programmed learning, presenting material in small steps and giving the learner feedback on their responses.
Technophobia
An excessive or irrational fear of, or aversion to, technology.
Telegraphic speech
The characteristic speech pattern of children roughly 18 months to 2 years old, in which only the essential content words of a sentence are used, while grammatical connectors such as “the,” “and” or “is” are typically omitted — for example, “want cookie” rather than “I want a cookie.”
Telekinesis
A term, coined by publisher Henry Holt, for the direct influence of mind over a physical object or system, unaccounted for by any known physical force — essentially synonymous with psychokinesis, though sometimes used more narrowly to refer specifically to the movement of physical matter.
Teleology
Within psychology, the study of psychological phenomena on the assumption that they serve some underlying goal or purpose, together with the attempt to identify what that purpose is.
Telepathy
The claimed direct communication between two minds, or knowledge by one person of another's thoughts, without relying on any of the ordinary recognised senses; a form of claimed extrasensory perception.
Territoriality
A concept developed mainly within ethology, describing the tendency of certain animal species to stake out and defend a territory for their own or their group's exclusive use, generally assumed to be an innate behaviour pattern in those species. Any apparently similar territorial behaviour in humans should be labelled with considerable caution, since there is no solid evidence that such behaviour is innate in human beings in the same sense. See also: crowding behaviour.
Thanatology
From thanatos, Freud's term for the death instinct: the interdisciplinary study of death, dying, and how people and societies understand and cope with them.
Thematic Apperception Test
A projective technique, developed by American psychologist Henry Murray, consisting of a series of ambiguous drawings (typically depicting one or more human figures in an undefined situation) about which the respondent is asked to construct a story. The recurring themes that emerge across these stories are then used to help identify underlying areas of emotional conflict or concern.
Thought-disorder
A significant disturbance in a person's normal patterns and organisation of thought, often regarded as one of the core symptoms of psychosis, particularly schizophrenia.
Totem
An anthropological term for a living creature, object, or its symbolic representation, revered by a particular group of people as a protective ancestral or spiritual figure, often central to that group's identity and rituals.
Tracking
The process of making continuous adjustments, particularly of the eyes, to follow a moving object; often assessed clinically in examining infants' visual development or in evaluating patients for possible brain damage.
Trait
Any relatively stable, enduring characteristic of a person's behaviour or personality, used as a basic building block in trait theories of personality.
Transactional analysis
A form of group therapy, developed by Eric Berne, in which the relationships and communications between group members are analysed in terms of interactions between three internal states — “parent,” “child” and “adult” — each person is understood to shift between.
Transfer of training
The phenomenon by which learning achieved in one situation carries over and influences performance in a different, related situation. This transfer can be positive (already knowing Spanish can make learning Italian easier) or negative (already knowing how to steer a car with a wheel can make it harder to learn to steer a boat with a tiller). See also: learning set.
Trauma
A significant physical or psychological shock resulting from an injury, violent incident, or other deeply distressing experience, with effects that can persist well beyond the event itself.
Trial and error learning
The gradual, step-by-step form of learning that occurs over repeated attempts, characteristic of much animal learning and a good deal of human learning, and the basic mechanism underlying most conditioning procedures. Considerably slower and more laborious than insight learning, in which a solution appears suddenly rather than through incremental trial and correction.
Definitions of terms used in psychology, psychometric testing and occupational assessment, organised alphabetically.
Saccadic movement
The rapid, jumping movement of the eyes from one fixation point to another, as occurs continuously during reading and general visual scanning.
Sample
A group of cases or individuals studied as representative of the larger population from which they were drawn, so that findings can be generalised beyond the sample itself. See also: biased sample, random sample.
Scapegoat
The target of displaced aggression or blame. In biblical tradition, a goat was symbolically sent into the wilderness once a year, on the Day of Atonement, carrying away the sins of the community. In modern usage, scapegoats are individuals or groups blamed for social frustrations or problems that are not, in fact, of their making.
Schema
A mental model, framework or structured pattern of knowledge through which new experiences are interpreted and organised. Central to Jean Piaget's account of how children make sense of the world at different developmental stages, and now widely used across cognitive psychology.
Schizoid
Relating to, or resembling features of, schizophrenia, though without necessarily meeting the full clinical criteria for the disorder — as in “schizoid personality.”
Schizophrenia
The most common category of psychosis, covering a wide range of symptoms and behaviours. The term comes from the Greek schizo (“split”) and phrenia (“mind”), a source of a near-universal popular misconception: “split mind” in the everyday sense of “split personality” actually describes multiple personality (dissociative identity disorder), an entirely different condition involving apparently separate personalities. The “split” in schizophrenia is instead between a person's thinking and feeling processes, disrupting the normal harmony between thought, emotion and action — so a person with schizophrenia might, for instance, show no emotion, or an incongruent emotion, while describing a tragic event. Difficulty communicating with others, delusions and hallucinations are also common symptoms.
Scotoma
A blind area within the visual field caused by damage to the retina or visual pathway, distinct from the small blind spot present in every normal eye where the optic nerve exits the retina.
Seashore test
A series of recorded tests assessing musical ability — pitch discrimination, rhythm, timbre and related skills — developed by American psychologist Carl Seashore.
Second-order conditioning
See higher-order conditioning — a form of classical conditioning in which a previously conditioned stimulus is used to condition a response to a new, second stimulus.
Selective attention
The deliberate focusing of attention on one particular stimulus or task, to the exclusion of other, competing stimuli in the environment. See also: cocktail party phenomenon.
Self
In humanistic psychology, a concept roughly equivalent to the ego in psychoanalytic theory: the part of the personality that maintains a continuous, conscious sense of its own identity over time.
Self-actualisation
According to Abraham Maslow, the ongoing drive to fulfil one's fullest potential and capacities, considered a hallmark of psychological health and the summit of his hierarchy of needs.
Self-concept
The full set of beliefs, perceptions and evaluations that together make up a person's overall view of themselves, including their self-image.
Self-esteem
The degree to which a person likes, values and feels worthy of respect as themselves.
Self-fulfilling prophecy
The phenomenon by which an expectation about one's own or another person's behaviour can, through its influence on how people act, actually bring that expected behaviour about — as demonstrated in the Rosenthal effect. See also: experimenter bias.
Self-image
The particular self a person believes themselves to be — a composite of many influences that may bear little resemblance to any objective assessment of that person, or to how others actually see them. Self-image begins forming very early in life and is, to a significant degree, rooted in early body image: an adult of normal or even above-average height may still privately think of themselves as small, because that was their relative size among peers when their self-image was originally formed. The judgements of significant other people also shape self-image profoundly, and these early-formed impressions can persist even as a person's actual social circumstances and the judgements others make of them change considerably in later life.
Self-serving bias
A form of the fundamental attribution error applied specifically to oneself — the tendency to attribute one's own successes to personal ability or effort, while attributing one's own failures to external circumstances.
Semantic differential
A technique developed by American psychologist Charles Osgood for studying how different people understand and relate to the same words or concepts. Participants rate a given term along several bipolar dimensions, such as good-bad or active-passive, and the resulting ratings are compared across individuals or groups.
Semantic memory
Memory for general factual knowledge and concepts, independent of the specific personal context in which it was learned — as distinct from episodic memory, memory for specific personally experienced events, though the two systems interact closely.
Semicircular canals
Three fluid-filled canals in the inner ear, oriented at right angles to one another, that detect head movement and relay information about balance and spatial orientation to the brain.
Senescence
A term used within developmental psychology to draw attention to the psychological stresses, conflicts and adjustments of old age and the ageing process, as well as its distinctive and potentially positive aspects.
Senile dementia
An older term for dementia occurring in old age, sometimes referred to popularly as “senility.” A progressive, degenerative condition, it includes, for example, the later stages of Alzheimer's disease.
Sensation
The immediate experience produced by the stimulation of a sense organ — the eyes, ears, skin and so on — and a necessary first step before the higher-level process of perception can occur.
Sensitivity training
A technique aimed at improving interpersonal communication and relationship quality within small groups, rooted in humanistic psychology and drawing on the methods and experience of group therapy. Group leaders encourage open, honest discussion of feelings within the group, in the hope that increased sensitivity to interpersonal dynamics will carry over into participants' relationships outside the group.
Sensorimotor stage
According to Jean Piaget, the first stage of cognitive development, spanning birth to around age 2. During this stage, the infant initially experiences themselves as the centre of the world, only gradually coming to distinguish between self and other; the stage's other major achievement is object permanence.
Sensory deprivation
A situation in which people are deprived of the ordinary level of sensory stimulation encountered in everyday life. Experimental studies isolating people from sensory input as far as possible in a laboratory have found that participants quickly become bored and, before long, begin to hallucinate — suggesting that when the brain has nothing external to process and make sense of, it may generate its own sensations and patterns instead.
Sensory memory
The very first stage of the memory process, lasting less than a second, during which raw information is briefly registered by the sense organs before either fading or being passed on for further processing. See also: short-term memory, long-term memory.
Separation anxiety
In psychoanalytic theory, an infant's fear of losing their mother or primary caregiver. The consequences of an infant actually losing a mother, or her love and attention, have received extensive research attention well beyond psychoanalysis. See also: maternal deprivation.
Serendipity
Named after the island of Serendip in the tale of Sinbad (popularised in English via Horace Walpole): the experience of discovering something valuable while searching for something else entirely — a pattern found, to varying degrees, in the careers of major figures in psychology and science, including Freud and Pavlov, as well as in the everyday experience of browsing a dictionary or encyclopedia.
Serial learning
Learning a body of material in a specific, fixed order or sequence, as opposed to learning discrete, unordered items.
Shaman
An anthropological term for a religious or spiritual specialist within a society who is believed to mediate between the human and supernatural worlds, often combining roles of healer, mystic and community guide.
Shame culture
A culture that relies primarily on the threat of shame and public ridicule, rather than internalised guilt, to regulate individual behaviour and maintain social order. Such a culture can be vulnerable to rule-breaking that goes undetected, since there is less internalised self-regulation to prevent it in private. Contrasted with guilt culture.
Shaping of behaviour
A technique used in operant conditioning in which any behaviour that approximates the ultimately desired response is initially rewarded, with the criteria for reward gradually narrowed over successive steps until the exact target behaviour is achieved.
Shell shock
The First World War-era term for the psychological condition now generally understood as battle fatigue, combat fatigue, or, in modern clinical terms, combat-related post-traumatic stress disorder.
Shibboleth
Originally a Hebrew word whose particular pronunciation was reportedly used by an ancient Israelite tribe to identify friend from foe; now used more generally for a word, phrase or custom that serves as a marker of belonging to a particular group or of being genuinely “in the know.”
Shock treatment
See electroconvulsive therapy — the more colloquial, and now largely outdated, name for the procedure.
Short-term memory
The second stage of the memory process, following sensory memory and preceding long-term memory, typically lasting up to about 30 seconds. During this brief window, information is either transferred into a more permanent long-term store or allowed to fade and be lost.
Sibling rivalry
Competition between children within the same family, most often for parental attention, affection or approval.
Signal detection theory
An alternative to the older concept of a fixed absolute threshold of sensation, proposing instead that a person's detection of a given stimulus (“signal”) depends jointly on the underlying sensitivity of their sensory system and their motivation, expectations and decision criteria for responding.
Significant other
A term from sociologist George Herbert Mead for a specific individual who holds particular personal importance to someone, especially in shaping their self-image — as opposed to the generalised other, representing society's expectations more broadly.
Skinner, B. F. (1904-1990)
The most celebrated and influential exponent of behaviourism, both as a scientific approach within experimental psychology and, more controversially, as a proposed basis for organising society. His signature technique, operant conditioning, built on the earlier work of Pavlov and Watson. Skinner set out the broader social implications of his behaviourist philosophy in influential popular works including the novel Walden Two and the non-fiction Beyond Freedom and Dignity.
Sleep centre
A region within the hypothalamus whose electrical stimulation induces sleep, and whose surgical removal (in animal studies) disrupts normal sleep patterns.
Sleep deprivation
Prolonged prevention of sleep eventually produces significant adverse effects, including hallucinations and disturbances of thought and behaviour. Some sleep and dream researchers argue that dreaming itself, specifically, is the most critical function being disrupted by sleep deprivation, noting that beyond the absence of dreaming, it is otherwise difficult to detect major physiological differences between sleep and simple restful wakefulness.
Sleeper effect
A term used in several related senses within the social psychology of attitude change, most often describing a shift in attitude or opinion measured some time after an initial study or persuasive communication — a phenomenon that can complicate the accuracy of opinion polling. It is also used for cases where a persuasive message becomes more, rather than less, influential after a delay, and to describe the gradual dissociation, over time, between a message's content and its original source, which can make people more receptive to a message from a source they initially distrusted.
Slip of the tongue
See parapraxis — an unintended verbal error, interpreted in psychoanalytic theory as a possible clue to unconscious material (a “Freudian slip”).
Social anthropology
The branch of anthropology concerned with studying social systems, institutions and cultures across different societies, historically with a particular focus on non-literate, small-scale societies.
Social cognition
An approach combining cognitive psychology and social psychology, which emerged prominently from the 1960s onward. Generally seen as part of the broader cognitive revolution, though with older roots reaching back to Gestalt psychology, it is chiefly concerned with how people process information, often with minimal cognitive effort, to make sense of their social world and social behaviour — including how people attribute causes to social behaviour, form stereotypes, and rely on cognitive heuristics.
Social cohesion
The overall attraction a group holds for each of its individual members, which helps bind the group together and maintain its stability over time.
Social comparison
The process of evaluating one's own attitudes, abilities and behaviour by comparing them against those of other people. Social psychologists have suggested that when people are uncertain how to act, think or feel in a given situation, they become more likely to look to others for cues and conform to the behaviour they observe.
Social constructionism
The theoretical position that people's understanding of reality is substantially shaped, or “constructed,” by their personal circumstances and social environment, rather than reflecting a single fixed, universal human nature or an entirely objective reality. The approach tends to emphasise social rather than purely individual explanations of psychological phenomena, and favours qualitative over quantitative research methods.
Social Darwinism
The application of Darwin's evolutionary theory of natural selection to human societies, holding that only the socially “fittest” individuals or groups survive and prosper. In practice, the theory has chiefly served, historically, as a way of justifying existing social and economic inequality by framing the wealthy and successful as having been naturally selected for that position — an application now widely regarded as a serious and harmful misuse of evolutionary theory.
Social distance scale
A measurement instrument designed to assess the degree of social closeness or intimacy a person is willing to accept in relation to members of a different group.
Social exchange theory
See exchange theory of friendship — the application of cost-reward reasoning to understanding social relationships.
Social facilitation
The stimulating, performance-boosting effect that the presence of other people — even simply their presence, without active involvement — can have on a person's behaviour and performance. The Hawthorne effect is a well-known illustration of the broader principle.
Social identity theory
The theory that people readily categorise others (and themselves) into in-groups and out-groups, and tend to find their own in-groups attractive because belonging to them boosts self-esteem. See also: social comparison.
Social interaction
The mutual, reciprocal influence that people have on one another's behaviour within a social setting, forming the basic unit of analysis for much of social psychology.
Social learning theory
A theory of personality and behaviour development, grounded in experimental learning research and associated principally with American psychologist Albert Bandura and his concept of modelling. It rejects both the unconscious drives central to psychoanalysis and the rewards-and-punishments framework of strict behaviourism as sufficient explanations on their own, emphasising instead the central importance of observational learning, particularly in children's development.
Social loafing
The tendency for individuals to exert less effort on a task when working as part of a group than when working alone, generally attributed to a diffusion of responsibility for the outcome across all group members.
Social norm
A pattern of behaviour expected of all members of a given society; one common way of defining what counts, socially, as “normal” behaviour.
Social psychology
The branch of psychology concerned with social life — the behaviour of people in groups, and the behaviour of individuals as shaped by social settings and other people.
Social science
Any academic field concerned with studying people as social beings, generally understood to include, to varying degrees, anthropology, economics, history, political science, psychology and sociology.
Social status
A person's position within a society's social hierarchy, defined relative to, and largely determined by, the judgements of other people.
Social stratification
The division of a society into distinct, hierarchically ordered social classes or strata, typically based on factors such as wealth, occupation, education and social prestige.
Socialisation
The lifelong process by which an individual becomes a functioning social being, learning the norms, values and expected behaviours of their society. Though ongoing throughout life, socialisation is considered especially formative during childhood, when society is chiefly represented to the child through parents and other family members.
Sociocentric
Regarding one's own society or culture as inherently superior to all others, and as the ultimate standard against which everything else should be measured. Closely related to ethnocentrism, and typically involving a degree of egocentricity projected onto the level of the group.
Sociology
The academic discipline concerned with the study of society in general, and of social organisation, institutions and relationships in particular.
Sociometry
A term and associated technique invented by American psychiatrist Jacob L. Moreno, designed to systematically measure and map what members of a group think and feel about one another.
Sociopathic personality
See antisocial personality — an older term, now generally superseded in clinical usage.
Sod's Law
The informal, humorous axiom that if something has the potential to go wrong, it eventually will — closely related to, and often used interchangeably with, Murphy's Law.
Somatising
A term used in psychotherapy for the process by which psychological stress or conflict manifests as physical bodily symptoms, as seen in psychosomatic illness.
Sour grapes reaction
Convincing oneself that something one cannot have was never really worth having in the first place. In clinical psychology, this pattern is generally termed rationalisation; in social psychology, it is understood as an attempt to resolve underlying cognitive dissonance.
Spaced practice
Any form of learning in which practice sessions are separated by intervals of time, though without necessarily arranging those intervals for maximum learning benefit, as distributed practice specifically aims to do.
Speech centre
A general term for brain regions particularly associated with the ability to produce and understand spoken language. See also: Broca's area, Wernicke's area.
Split personality
See multiple personality — the popular but often misleading term for what is now called dissociative identity disorder.
Split-brain technique
A surgical procedure severing the connections between the brain's two hemispheres, historically used, for instance, to relieve severe, otherwise uncontrollable epileptic seizures. People who have undergone this surgery lose the ability to integrate sensory information and coordinate movement across both sides of the body, since the two hemispheres can no longer directly communicate; each hemisphere instead appears to take over some functions independently, in effect functioning as two separate, semi-autonomous processing systems within one brain. These striking effects are the direct result of the physical surgical procedure and have no connection whatsoever to psychological phenomena such as dual, multiple or split personality, or to schizophrenia — conditions with entirely different underlying causes, despite the superficial similarity in popular language.
Spontaneous recovery
In conditioning, the reappearance of a previously extinguished conditioned response after a period of rest, even without any further pairing of the conditioned and unconditioned stimuli.
SQ3R
A long-established study method for learning from textbooks, standing for its five steps: Survey the material broadly, form Questions about its content, Read the material thoroughly, Recite the key points from memory, and Review the material again afterward.
Statistical significance
The probability that a study's results could have arisen purely by chance rather than reflecting a genuine effect. By current scientific convention, a probability of 5 in 100 or less (a significance level of 0.05) is generally considered the threshold for results to be regarded as statistically significant. See also: null hypothesis.
Statistics
A branch of applied mathematics used to analyse data gathered in the study of behaviour, allowing researchers to evaluate their findings and draw inferences that extend beyond the specific sample studied to a wider population.
Stereoscopic vision
The perception of depth and distance arising mainly from the brain's merging of the two slightly different images projected onto the retina of each eye, due to their separated positions on the face.
Stimulus generalisation
In studies of conditioning, the principle that a response conditioned to occur in reaction to a particular stimulus will also tend to occur, to some degree, in response to similar stimuli. Compare with stimulus discrimination, in which an organism learns to respond only to the specific original stimulus.
Strabismus
Commonly known as a squint: a condition caused by poor coordination of the eye muscles that prevents both eyes from focusing on the same point simultaneously.
Stranger anxiety
A fear response to unfamiliar people, particularly unfamiliar faces, that typically emerges in infants at around 8 months of age as part of normal social-cognitive development.
Stream of consciousness
A term introduced by nineteenth-century American psychologist William James (whose brother, novelist Henry James, is considered one of the pioneers of “stream of consciousness” fiction), intended to emphasise the continuous, flowing nature of conscious experience, in contrast to a competing tendency in early psychology to break consciousness down into discrete, separately studied units.
Stress
Physical and psychological strain, typically persisting over a period of time, that threatens a person's or animal's ongoing ability to cope effectively with a given situation or set of demands.
Stroboscopic effect
A visual illusion of continuous movement produced by a rapid sequence of separate, stationary images, as in film. See also: phi phenomenon. The term is also used more specifically for the effect produced when a genuinely moving object is illuminated by a rapidly flashing (strobe) light, which can make its motion appear frozen, slowed or reversed.
Stroking
In transactional analysis, any act that conveys caring recognition of, and attention to, another person — by analogy with the literal physical stroking and handling that supports healthy development in infants.
Strong Vocational Interest Blank
A widely used questionnaire measuring a person's interests, with results compared against the typical interest profiles reported by people already working successfully in various occupations, in order to suggest well-matched career directions.
Subconscious
Something not currently in full conscious awareness but readily capable of being brought into consciousness. Most often used loosely, in a general or physiological sense, to describe a point along the continuum running from full waking awareness to deep sleep; its nearest psychoanalytic equivalent is the preconscious, and it should not be confused, as it commonly is in popular usage, with the unconscious, a distinct and more clinically specific concept.
Subculture
A distinct culture existing within a larger, broader culture, sharing many of that parent culture's core features while retaining its own particular characteristics, practices or values.
Subjective
Describing something that exists within one's own individual experience and is not directly accessible to or verifiable by others. Contrasted with objective.
Sublimation
In psychoanalysis, a defence mechanism in which unacceptable unconscious impulses are redirected into socially and consciously acceptable forms of activity or expression. Freud regarded sublimation as society's principal, healthiest way of managing the underlying tension created by repression, and it is generally considered the most socially constructive of the classic defence mechanisms.
Superego
Literally, from the Latin, “over the I”: in Freud's model of personality, one of the three main structural components, alongside the ego and the id. Like the id, with which it is perpetually in tension, the superego operates largely at an unconscious level. It represents the internalisation of restrictions on the id's impulses, reflecting the moral standards and behavioural expectations instilled by parents and by society more broadly — functioning, in effect, as the personality's conscience.
Superordinate goal
In social psychology, a goal that cannot be achieved by any one group acting alone, requiring the active cooperation of two or more otherwise separate or competing groups. Deliberately introducing such shared goals is regarded as an effective way of reducing intergroup conflict and improving relations between groups.
Surrogate
A person or thing that psychologically takes the place of another — for example, an older sibling functioning as a mother surrogate, or a therapist functioning, in a patient's mind, as a father surrogate. In psychoanalysis, the term is also used for a person or object, often appearing unconsciously in a dream, whose function is to disguise the true identity of whoever or whatever is actually generating the underlying powerful feelings involved.
Survey research
A research technique for gathering data from large numbers of people through the use of structured questionnaires, typically combined with systematic sampling methods to ensure the results generalise to a wider population.
Survival value
A physical or behavioural characteristic that increases the likelihood that an individual organism, or an entire species, will survive and successfully reproduce within its environment.
Symbiosis
Originally a biological term for the permanent, mutual dependence of two different organisms on each other for survival. Sometimes used more loosely, and metaphorically, by psychologists to describe two people whose relationship appears to sustain and reinforce each other's individual psychological difficulties. See also: folie à deux.
Symbolic interaction
A sociological approach to social psychology emphasising the central role played by language, gesture and other social symbols in people's conscious efforts to construct their sense of self and their understanding of the world, treating distinctively human qualities as products of this ongoing social interaction rather than as fixed, pre-social givens.
Sympathy
The capacity to genuinely feel, to some degree, what another person is feeling — an emotional, shared experience, as distinguished from empathy, which is generally treated as a more cognitive act of understanding another's feelings without necessarily sharing them.
Synaesthesia
The experience of a sensation in one sensory modality being triggered by stimulation of a different one — for example, perceiving music as having distinct colours, or associating particular numbers with particular colours.
Systems theory
A theoretical framework treating a “system” as any set of interconnected elements forming an organised, coherent whole — such as the central nervous system or a kinship system — and seeking to identify general principles that apply across many different kinds of systems by comparing their underlying structures and functions.
Definitions of terms used in psychology, psychometric testing and occupational assessment, organised alphabetically.
R
The symbol conventionally used for the most common correlation coefficient, measuring the strength and direction of a relationship between two variables.
Race
An anthropological term for a proposed biological subdivision of humanity based on shared genetic ancestry, associated with common physical characteristics such as skin colour and facial structure. Modern genetics has shown there is no such thing as a biologically “pure” race; every physical characteristic occurs, to varying degrees, across all major human population groups, and genetic variation within any so-called racial group is generally far greater than variation between groups. Claims that a particular minority group is inherently intellectually inferior to a majority group — made about different groups at different points in history — have never been supported by solid evidence, and there is substantial evidence against them; moreover, even setting that aside, intelligence tests themselves have long been shown to carry educational, cultural and social biases against minority groups.
Racial memory
A concept, closely related to Carl Jung's collective unconscious, proposing that certain feelings, patterns of thought and fragments of experience are transmitted across generations within humanity as a whole and continue to shape mind and behaviour, even though the individual has no personal memory of their origin.
Random sample
A sample drawn from a population in such a way that every member of that population has an equal chance of being selected, allowing researchers to generalise findings from the sample back to the wider population with reduced risk of the sample being a biased sample.
Randomise
In experimental psychology, the random assignment of participants to different groups, or the random ordering of stimuli presented to participants, so that any individual differences or order effects are evenly spread across conditions and do not distort the experiment's results.
Rapid eye movements
The rapid, jerking movements of the eyes that occur during REM sleep, closely associated with vivid dreaming. See also: paradoxical sleep.
Rational-emotive therapy
A form of psychotherapy, closely related to behaviour therapy, developed by American psychologist Albert Ellis. It directly confronts the irrational beliefs thought to underlie a person's emotional and behavioural difficulties, actively challenging the patient to replace them with more rational, realistic ways of thinking.
Reactance theory
A concept in social psychology holding that when people feel their freedom of choice is being restricted or their decisions manipulated, they tend to react by finding the restricted option more attractive, or by adopting a position opposed to the one being pushed on them, as a way of reasserting their autonomy. See, for example: Romeo and Juliet effect.
Reaction formation
In psychoanalysis, a defence mechanism in which a person unconsciously adopts attitudes or behaviour that are the direct opposite of an unacceptable underlying impulse or feeling — for example, responding to underlying hostility toward someone with exaggerated warmth and solicitude toward them.
Reaction time
The interval of time that elapses between the presentation of a stimulus and a participant's response to it, widely used as a basic measure in experimental and cognitive psychology.
Reality principle
In psychoanalysis, the ego's modification of the pure pleasure principle governing the id: the ego's way of balancing what the id wants against what is actually achievable given the practical constraints of the external world.
Reality testing
In psychoanalysis, the ego's ongoing, practical effort to act in accordance with the reality principle, checking internal wishes and impulses against the actual constraints and possibilities of the external world.
Recidivism
The tendency to relapse into previous behaviour, most often used to describe repeated criminal offending after punishment or treatment, though also applied more broadly to the recurrence of psychological disturbance.
Reification
The error of treating an abstract concept or idea as though it had a concrete, independent, objective existence in the real world — for instance, treating “intelligence” as a physical thing rather than a theoretical construct.
Reinforcement
The process of strengthening the likelihood that a given behaviour will recur, by following it with a rewarding consequence; the foundational mechanism underlying all forms of conditioning. See also: positive reinforcement, negative reinforcement, intermittent reinforcement.
Releaser
In ethology, a specific stimulus that triggers an automatic, largely fixed behavioural response in an organism. See also: innate releasing mechanism.
Reliability
A statistical measure of a test's internal consistency — the extent to which it can be expected to produce the same, or very similar, results if administered again on a different occasion, under similar conditions.
REM sleep
See rapid eye movements and paradoxical sleep — the stage of sleep most closely associated with vivid dreaming.
Replication
Repeating an experiment in exactly the same way it was originally conducted (though possibly at a different location and with different participants), in order to confirm whether the original findings hold up. Although replication is widely praised in principle within psychology, it has historically been relatively rare in practice, since there is comparatively little academic reward or career incentive for researchers to conduct and publish replication studies rather than original research.
Repression
In psychoanalysis, a defence mechanism and one of the most central concepts in Freudian theory: the process of pushing disturbing feelings and impulses arising from the id out of conscious awareness entirely, submerging them in the unconscious, where they continue to exert influence, often causing psychological trouble. Repression is considered central to many neuroses, most strikingly certain forms of amnesia; Freud regarded repression as the psychological price paid for living in civilised society, and psychoanalysis — by making the unconscious conscious — as the principal way of coming to terms with that cost. Contrast with inhibition, a related but distinct process.
Resistance
In psychoanalysis, a term describing both the reluctance of repressed unconscious material to surface into conscious awareness, and the parallel reluctance of the patient (or “analysand”) to allow the analyst's probing to successfully uncover the underlying areas of unconscious conflict.
Response bias
A mental set or tendency to respond in a particular, consistent way to certain kinds of questions or issues, regardless of their actual content — for example, a tendency to always agree with statements on a questionnaire.
Restricted code
British sociolinguist Basil Bernstein's term for a relatively inarticulate communication style, made up of short, often incomplete phrases and carrying comparatively limited explicit information — said to be more typical of working-class parent-child communication. Contrasted with elaborated code.
Retina
The light-sensitive inner surface of the eyeball, containing photoreceptor cells that detect visual images and transmit them as neural signals, via the optic nerve, to the brain.
Retrieval
The act of successfully recalling stored information from long-term memory back into conscious awareness.
Retroactive inhibition
The detrimental effect that later learning can have on the recall of material learned previously. Compare with proactive inhibition, in which earlier learning instead disrupts recall of later material.
Retrograde amnesia
The inability to recall events from the period immediately preceding the injury, trauma or other event that caused the amnesia.
Retrospective falsification
The unintentional, non-deliberate distortion of memories of past experience, generally not attributed to unconscious motivated processes (unlike, for example, repression), but rather to the ordinary, reconstructive nature of memory itself.
Risky shift
A form of group polarisation in which people arrive at riskier decisions under the influence of group discussion than they would have reached individually; the opposite of the cautious shift.
Rogers, Carl (1902-1987)
A leading figure in humanistic psychology and a chief proponent of non-directive therapy, most notably through his own influential approach, client-centred therapy, which emphasised unconditional positive regard for the client.
Role
In social psychology, the pattern of behaviour expected of a particular person occupying a particular position within a given social situation — such as the role of teacher, parent, or manager.
Role playing
Used in two related senses: acting out the part of another person within a therapeutic or experimental setting, in order to gain insight or practise a skill; or deliberately performing a particular social role for a calculated effect on others.
Romeo and Juliet effect
A finding in social psychology that parental or external opposition to a young couple's relationship can, counterintuitively, strengthen rather than weaken their romantic attachment — named for Shakespeare's star-crossed lovers, and closely related to reactance theory.
Rorschach test
The most famous of all projective techniques, frequently referenced (and parodied) in popular culture. It consists of ten standardised inkblot images, developed by Swiss psychiatrist Hermann Rorschach, to which a respondent's free associations are examined against categories of response that have been standardised through extensive use over many decades. No clinician would base a diagnosis solely on Rorschach results, but many clinical psychologists still regard it as a useful initial step in a broader assessment.
Rosenthal effect
A form of experimenter bias, or self-fulfilling prophecy, operating within a social setting, first demonstrated by psychologist Robert Rosenthal. In a well-known study, Rosenthal led a group of teachers to believe that certain students in their classes had unusually high IQs and were expected to excel that year; those students did indeed go on to perform better, even though they had, in reality, been of entirely average measured ability — illustrating how an authority figure's expectations can shape outcomes. Also known as the Pygmalion effect.
Rote learning
Learning achieved purely through repetition, without any attempt to understand, organise or find deeper meaning in the material being learned. Contrast with elaborative rehearsal.
Definitions of terms used in psychology, psychometric testing and occupational assessment, organised alphabetically.
Q-sort
A technique for assessing personality traits or attitudes in which a person is given a large number of descriptive statements — about themselves, or someone else — and sorts them into piles reflecting how strongly each statement applies.
Qualitative methods
Research methods concerned more with the depth, richness and meaning of the data collected than with strict experimental control, quantity of data, or the sophistication of statistical analysis. Participant observation and open-ended, unstructured interviews are among the most common examples in psychological research. Compare with quantitative methods.
Quantitative methods
Research methods concerned primarily with the precision and generalisability of the data collected, typically at the cost of some of the richness of content that qualitative methods can capture. The controlled experiment and structured questionnaire are the most common examples in psychological research.
Quartile
One of three points that divide a frequency distribution into four equal parts, each containing a quarter of the total scores.
Queuing
A term sometimes used to describe one way the mind handles sensory overload: by placing all but one of several competing stimuli “on hold” until the currently attended stimulus has been fully processed.
Quota sampling
A sampling method in which data is deliberately collected from each of several subgroups within a population, in proportions intended to reflect that population's known composition.
Definitions of terms used in psychology, psychometric testing and occupational assessment, organised alphabetically.
Paired associates
A technique used in learning research in which words are presented to a participant in pairs; afterward, the participant is given only the first word of each pair and asked to recall the second.
Palsy
A form of paralysis, often accompanied by uncontrollable trembling, resulting from damage to the nervous system.
Paper-and-pencil test
Any test or assessment procedure, including many projective techniques, that requires written answers rather than, for example, verbal responses or performance-based tasks.
Paradigm
A detailed model or example that serves as a pattern for understanding a broader class of phenomena; in the philosophy of science, a term popularised by Thomas Kuhn for the dominant theoretical framework accepted within a field at a given time.
Paradoxical sleep
A stage of sleep marked by high levels of electrical brain activity alongside deeply relaxed muscles and difficulty waking the sleeper; the brain-wave pattern recorded resembles that of someone awake, and the stage is typically accompanied by the rapid eye movements associated with vivid dreaming (REM sleep).
Parakinesis
A term used in parapsychology for the apparent movement of physical objects by unexplained means, without any conventional physical force being applied.
Parallax
The perceived movement of objects relative to one another as the eyes or head move: objects nearer than the point of fixation appear to move in the opposite direction to the movement, while objects beyond it appear to move in the same direction, with nearer objects appearing to move faster. An important cue used in depth perception.
Parallel distributed processing
See connectionism — the model of cognitive processing as operating simultaneously across a distributed network, rather than in a single sequential stream.
Parameter
Mathematically, a constant within an equation that determines the specific shape of a curve; in psychology, a constant that shapes the curve of a particular psychological function, such as a learning curve. Often confused, incorrectly, with “perimeter.”
Parametric statistics
Statistical methods and tests that assume the underlying data follow a normal distribution.
Paranoia
A psychotic condition characterised by delusions, especially delusions of grandeur and delusions of persecution. Outside the specific content of these delusions — which a person may defend vigorously and, at times, with superficially plausible reasoning — someone with paranoia can often function and behave quite normally.
Paranormal
Describing psychological events or experiences that appear not to be explicable by currently understood scientific principles; the central subject matter of parapsychology.
Parapraxis
Apparent minor errors of behaviour, such as forgetting a familiar name or a slip of the tongue; in psychoanalytic thought, such slips are known as Freudian slips and are held to reveal underlying unconscious material.
Parapsychology
The branch of study concerned with paranormal phenomena, particularly claims of extrasensory perception, and with attempting to extend recognised scientific methods and principles to account for them. Between 1927 and 1965, researcher J. B. Rhine directed an influential research laboratory at Duke University investigating such phenomena; the main criticism of this body of work is that experiments claiming to demonstrate paranormal effects have generally failed to be replicated by independent researchers outside the original lab. See also: replication.
Parkinson's Law
The wry management maxim that work expands to fill the time available for its completion, proposed by British writer C. Northcote Parkinson.
Part method
A learning technique in which material is broken down into smaller sections, learned separately, and then combined into the whole. Compare with whole method.
Partial reinforcement
See intermittent reinforcement — rewarding a response only some of the time rather than every time.
Participant observation
A research technique, used across the social sciences, in which a researcher becomes an accepted, embedded member of the group they wish to study, observing behaviour from within rather than from a detached outside vantage point.
Passive-aggressive personality
A personality pattern in which anger and hostility are expressed indirectly, often through oscillating between extreme dependence on, and covert aggression toward, other people — for example, someone who is chronically, passively late to meetings with people they resent, provoking anxiety and frustration in others without open confrontation.
Paternalism
Treating adults as though they were children, by withholding from them the information, autonomy or power needed to make decisions that affect their own lives, ostensibly for their own good.
Pathological
Abnormal in the specific sense of being diseased or disordered, rather than merely unusual or statistically rare.
Patriarchy
A society or social group in which men hold the primary positions of authority and leadership. Contrast with matriarchy.
Patrilineal
Describing a society or social group in which lineage, descent or inheritance is traced through the father's side of the family. Contrast with matrilineal.
Pattern recognition
The cognitive (and, in artificial systems, computational) process of identifying meaningful patterns, shapes or regularities within a stream of sensory input or data.
PDP
An abbreviation for parallel distributed processing — see that entry.
Peak experience
In humanistic psychology, a rare, intensely powerful moment of emotional and spiritual fulfilment in which a person feels a profound sense of unity with themselves and the world — considered by Abraham Maslow to represent a moment of self-actualisation.
Pecking order
Originally, the hierarchy of dominance formed among farmyard hens through repeated pecking, with the most-pecked hen occupying the lowest status. Now used loosely, and somewhat imprecisely, to describe status hierarchies within human groups.
Pediatric
See paediatric — relating to the medical care of infants and children.
Peer group
A social group whose members interact on a broadly equal footing, typically of similar age or status — a concept especially significant during childhood and adolescence, when peer influence on behaviour and identity is particularly strong.
Pellagra
A nutritional deficiency disease (caused by inadequate niacin) whose most visible symptom is a characteristic skin condition, but which can also produce psychological symptoms, particularly depression, alongside gastrointestinal and neurological effects.
Penology
The study of criminal behaviour, punishment, and the treatment and rehabilitation of offenders within the justice system.
Percentile
In statistics, one of the hundred equal divisions of a ranked distribution of scores; the ninetieth percentile, for instance, is the score below which 90 per cent of all scores in the distribution fall.
Perception
The process by which the brain receives the continuous flow of sensory information from the sense organs and organises this raw input into a coherent, meaningful understanding of the surrounding environment.
Perceptual defence
A mechanism by which a person unconsciously protects their ego from unpleasant or threatening perceptions, either by misperceiving them as less threatening or unpleasant than they actually are, or by failing to consciously perceive them at all.
Perseveration
The tendency for a particular thought, word or behaviour to recur repeatedly, even in the absence of any clear triggering stimulus and despite serving no obvious ongoing purpose; often associated with certain forms of brain damage.
Person perception
The process by which people form initial impressions of others and then progressively build them out into a fuller, more coherent overall judgement of that person's character.
Persona
From the Latin word for a theatrical mask: Carl Jung's term for the conscious, outward-facing aspects of personality that a person presents and employs in everyday social interaction, as distinct from their deeper, more private inner self.
Personal space
In social psychology, the area immediately surrounding a person that they experience as psychologically “theirs,” such that any uninvited intrusion into it tends to be perceived as hostile, threatening or simply uncomfortable. The size of this preferred space varies considerably between individuals and across cultures. Not to be confused with territoriality, which concerns a fixed physical location rather than a zone that travels with the person.
Personality
The sum total of the factors that make a given human being both distinctly individual and recognisably human — the patterns of thinking, feeling and behaving shared broadly across humanity, combined with the particular configuration of these elements that makes each person unique. Personality theorists generally emphasise both the integrated, dynamic nature of personality as a whole and the significant role of unconscious processes, which may be largely hidden from the individual themselves while remaining at least partly visible to other people.
Peter Principle
A satirical management observation, from Laurence J. Peter, that in a hierarchy people tend to be promoted based on their success in their current role until they reach a level at which they are no longer competent — and then remain stuck there.
Petit mal
See epilepsy — the milder form of epileptic seizure, producing only brief lapses in awareness rather than full convulsions.
PGR
An abbreviation for psychogalvanic reflex, the American equivalent of the British term galvanic skin response.
Phantom limb
The persistent sensation of feeling, including sometimes pain, in a limb that has been amputated. Proposed explanations include the slow adjustment of a person's existing self-image or body schema to the sudden physical change, and the possibility that neural pathways originally linking the missing limb to the brain remain active in some altered form.
Phenomenology
A philosophical approach advocating the direct study of conscious experience through careful introspection, as it presents itself to a particular observer, without imposing external theoretical assumptions onto that experience.
Phenomenon
Anything that presents itself to, or can be perceived by, an observer — any occurrence or fact capable of being directly observed or experienced.
Phenotype
The observable outcome of the interaction between a person's genotype (their inherited genetic potential) and their environment. Since a person's underlying genetic potential can never be directly observed — only its expression in actual behaviour and characteristics — everything we can observe about a person, from before birth onward, is technically a phenotype.
Phenylketonuria
A serious, hereditary form of intellectual disability caused by the body's inability to properly metabolise the amino acid phenylalanine, which then accumulates to toxic levels; now routinely screened for in newborns and managed through strict dietary control.
Phi phenomenon
The perceptual impression of movement created by a rapid, well-timed sequence of otherwise static visual stimuli — in its simplest form, two lights flashed on and off in quick succession, with the right interval between them, creating the illusion that a single light is moving between the two points. This illusion underlies the perceived movement in film, animation and neon signage, and was identified at the start of the twentieth century by the earliest Gestalt psychologists, shortly after the emergence of the film industry.
Philosophy
The systematic, disciplined attempt to understand the fundamental nature of reality, knowledge, ethics and existence, using reasoned argument rather than empirical experiment alone.
Phobia
An excessive, persistent and irrational fear of a specific object, activity or situation, generally regarded as a form of anxiety disorder.
Photographic memory
See eidetic imagery — the rare capacity, most commonly observed in children, to retain and recall an unusually detailed and vivid visual image of a scene after only brief exposure.
Phrenology
A now-discredited theory, first proposed in the eighteenth century, holding that a person's intellectual and psychological abilities could be assessed by examining the bumps and contours of their skull, on the assumption that specific brain regions governed specific abilities and that larger regions (and therefore larger corresponding bumps) meant greater ability in that area. Though now regarded as pseudoscience, phrenology is credited with helping to popularise the broader, ultimately valid idea that specific brain regions are linked to specific psychological functions.
Physiognomy
Historically, the now-discredited practice of attempting to infer psychological characteristics from the structure of a person's face, sometimes practised alongside phrenology; the term today refers more neutrally simply to a person's facial features and structure.
Physiological psychology
The branch of psychology concerned with the physiological, particularly neural and hormonal, processes that underlie behaviour and mental experience.
Phylogeny
The evolutionary history and development of an entire species over time. Contrast with ontogeny, the developmental history of a single individual organism.
Pilot study
A small-scale trial run of an experiment or survey, conducted to assess whether a larger, full-scale version is worth pursuing, and often used specifically to test and refine the proposed research methodology.
PK
An abbreviation for psychokinesis — see that entry.
PKU
An abbreviation for phenylketonuria — see that entry.
Placebo
An inactive substance, disguised to appear identical to an active treatment — for example, a sugar pill given to the control group in a drug trial, or to a patient who will not benefit medically from an active drug but psychologically benefits from feeling they are receiving treatment. See also: placebo effect.
Placebo effect
The measurable positive response people show to an inactive placebo treatment, as though it were pharmacologically active — for instance, patients reporting feeling better after being given a sugar pill with no active ingredient. The term is sometimes extended more broadly to describe any positive response people show simply from feeling that they are being attended to or cared for, at which point it closely overlaps with the Hawthorne effect.
Plantar reflex
The automatic downward curling of the toes when the sole of the foot is stroked, which typically replaces the earlier Babinski reflex at around age two as the nervous system matures.
Plateau
See learning plateau — a temporary flattening in the rate of improvement during skill acquisition.
Play therapy
The use of structured or unstructured play within psychotherapy with children, both to aid diagnosis and as a treatment in its own right: the child is encouraged, through play, to achieve a catharsis of emotions that they may not yet have the verbal capacity to express directly.
Pluralistic ignorance
A social situation in which most individuals privately doubt or reject a belief or norm that they nonetheless believe, mistakenly, is held by everyone else in their group — leading each person to conform outwardly to a consensus that, in reality, barely exists.
Poggendorff illusion
A visual illusion in which a straight diagonal line, interrupted by two parallel vertical bars, appears to be misaligned or discontinuous even though it is, in fact, perfectly straight.
Polymorphism
The process, in some organisms such as frogs or butterflies, of passing through distinctly different physical forms over the course of development — for example, from larva to adult.
Population
In statistics, the total set of cases or individuals from which a smaller sample is drawn for study, and about which the researcher ultimately wishes to draw broader conclusions.
Positive reinforcement
In conditioning, the strengthening of a given response by following it with a rewarding consequence.
Positivism
The philosophical position that genuine scientific knowledge is limited strictly to what can be directly observed and empirically verified, excluding speculation about unobservable causes or metaphysical claims.
Possession
The subjective feeling of being taken over or controlled by an external force or entity. In Western culture, this experience is generally treated as a symptom of psychosis; in other cultural and religious contexts, closely related experiences are understood as religious ecstasy or spiritual possession.
Post-hypnotic suggestion
An instruction given to a person while under hypnosis that they carry out after emerging from the hypnotic trance, typically without any conscious awareness of where the instruction originated.
Post-modernism
A broad intellectual position holding that the detached, purely objective observer assumed by traditional Western science and scholarship does not really exist — that all observation and knowledge are shaped by the observer's social and cultural position. Within psychology, this view is reflected particularly in social cognition research and in social constructionism.
Postconventional morality
The third and highest level in Lawrence Kohlberg's stage theory of moral development, at which moral behaviour is governed not by fear of punishment or by social convention, but by a self-chosen, consciously reasoned system of ethical principles. Kohlberg's research suggested that not everyone reaches this level of moral reasoning.
Postpartum depression
Depression occurring in the period following childbirth, thought to be caused by a combination of hormonal changes, sleep deprivation, and the psychological and social demands of new parenthood.
Potlatch
A ceremonial custom among Indigenous peoples of the Pacific Northwest Coast, including the Kwakwaka'wakw, involving the ritual giving away or destruction of personal property as a means of displaying and achieving social status. The term is occasionally borrowed in social-science writing to describe conspicuous, status-driven consumption in other cultures, including modern Western society.
Prägnanz
In Gestalt psychology, the principle that perception tends toward simplicity, harmony, meaningfulness and the best possible “fit” or “goodness” of form — for example, a battered old coin glimpsed in dim light will still tend to be perceived as a simple, regular circular object.
Precognition
A claimed form of extrasensory perception in which a person appears to have knowledge of a future event that could not have been logically inferred or predicted through ordinary means.
Preconscious
In psychoanalysis, mental content that is not present in conscious awareness at a given moment but that can be readily and deliberately recalled when needed. Compare with the unconscious, whose contents are not so easily accessible.
Predictive validity
See construct validity — specifically, the extent to which a test's scores successfully predict a person's future performance or outcomes on a related measure.
Prejudice
An attitude, opinion or belief, held with strong emotional conviction, that remains largely resistant to reasoned argument or contrary evidence. Though the term can technically apply to positive as well as negative pre-judgements, it is used almost exclusively in a negative sense, particularly regarding unfair judgements of social or ethnic groups.
Preoperational stage
The second of Jean Piaget's stages of cognitive development, spanning roughly ages 2 to 7, during which a child's thinking is intuitive rather than logical, and is characterised by magic thinking, a tendency toward anthropomorphism, and egocentricity.
Propositional representations
A widely used concept in cognitive psychology, sometimes described as “the language of the mind”: abstract, language-like symbolic units thought to form a universal underlying code in which thought and reasoning occur, independent of a person's specific native spoken language.
Presentation of self
A concept associated with Canadian sociologist Erving Goffman. See impression management.
Pretest
See pilot study — a preliminary, small-scale trial of a research procedure.
Prevision
A term closely related to precognition, used within the study of extrasensory perception for the claimed experience of directly “seeing” future events, popularly referred to as “second sight.”
Primacy effect
The finding that, other things being equal, the first item or items in a sequence tend to be remembered better than those in the middle. Compare with recency effect, the corresponding advantage for the most recent items.
Primal therapy
A form of psychotherapy developed in the United States by Arthur Janov, in which the therapist first deliberately intensifies a patient's distress, then encourages them to relive painful childhood feelings that were never fully expressed at the time. Releasing these feelings through an intense, cathartic “primal scream” is claimed to clear the way for healthier adult psychological functioning, though the approach lacks strong scientific support.
Primary attachments
The earliest and, typically, most enduring emotional bonds a person forms with others, usually with parents or primary caregivers in infancy.
Primary colours
The small set of colours that can be combined to produce the full range of other hues: in traditional usage, blue, yellow and red, along with black and white, though the specific set used varies by context (for instance, additive light versus pigment mixing).
Primary process
In psychoanalysis, the unconscious operations of the id, governed entirely by the pleasure principle, in its constant drive to find some way of achieving immediate gratification for its underlying needs and impulses.
Principle of parsimony
See Occam's razor — the preference for the simplest adequate explanation among competing alternatives.
Prisoner's dilemma
A scenario drawn from game theory, widely used by social psychologists to study bargaining and cooperative behaviour. Two suspects are arrested and questioned separately: if one confesses and the other does not, the confessor goes free while the other takes the full blame; if both confess, both receive a moderate sentence; if neither confesses, both benefit from a lighter outcome than if both had confessed — yet each has an individual incentive to confess regardless of what the other does, creating a tension between individual and collective rationality.
Proactive inhibition
The detrimental effect that earlier learning can have on the recall of material learned subsequently. Compare with retroactive inhibition, in which later learning instead interferes with recall of earlier material.
Probability
In statistics, a numerical measure of how likely a given event is to occur, relative to the likelihood of alternative possible events — for example, the probability of rolling any particular number on a fair six-sided die is one in six.
Procedural knowledge
Practical, “how-to” knowledge — the conscious or unconscious knowledge of how to perform an action or skill. Compare with declarative knowledge, factual “knowing that” knowledge.
Programmed learning
A system of self-paced instruction, grounded in the principles of operant conditioning, in which material to be learned is broken into small, sequential steps, with the learner given feedback on their mastery of each step before moving to the next.
Projection
In psychoanalysis, a defence mechanism in which a person unconsciously attributes to other people feelings or impulses that are actually their own, but which are too threatening to the ego to be consciously acknowledged as one's own.
Projective techniques
Assessment procedures designed to uncover a person's unconscious motivations, anxieties and conflicts by presenting them with relatively unstructured, ambiguous stimuli — as in the Rorschach inkblot test or the Thematic Apperception Test — onto which the respondent is thought to unconsciously project material that could not otherwise be directly and consciously acknowledged.
Proprioceptors
Sensory receptors that provide the brain with information about the body's own movement, position and orientation in space. Found in the semicircular canals of the inner ear, where they contribute to balance, and in the muscles and joints, where they produce kinaesthetic sensation.
Protocol
The original, detailed written record of an experiment, or the notes and materials generated during a clinical interview, diagnosis or course of treatment.
Proximity
See contiguity and continuity — Gestalt principles concerning how closeness in space or time influences perceptual grouping.
Proximodistal
Literally “close to distant”: describes the pattern of physical maturation in humans and animals in which development proceeds from the central axis of the body outward toward the extremities. See also: cephalocaudal, the corresponding head-to-tail developmental pattern.
Psyche
The ancient Greek term for the animating life force, historically translated first as “soul,” later as “mind,” and in some modern usage as “self” — the root of terms such as psychology and psychiatry.
Psychedelic
A term applied to drugs, such as certain hallucinogens, that appear to intensify perception and expand consciousness in dramatic ways; by extension, also applied to colour schemes, lighting or art intended to evoke similar sensory effects.
Psychiatrist
A licensed physician who specialises in psychiatry, the medical treatment of mental illness, and who is qualified, unlike most psychologists, to prescribe medication.
Psychiatry
The branch of medicine concerned with the diagnosis and treatment of mental illness. Psychiatry's subject matter overlaps substantially with clinical psychology, but the two differ in training and orientation: psychiatrists are trained as physicians, with a medical model of psychological disturbance and the ability to prescribe medication, whereas clinical psychologists typically have no medical training, cannot prescribe drugs, and are more likely to view normal and abnormal behaviour as lying along the same continuum rather than being categorically distinct.
Psychic
In general use, relating to the properties of the mind; in popular usage, describing a person claimed to possess spiritual, telepathic or other extrasensory abilities.
Psychic determinism
The theory that no psychological event, thought or behaviour is truly accidental or random, but always has a definite underlying cause, even if that cause is unconscious and not apparent to the person themselves. Freud proposed this as a foundational, guiding principle of psychoanalysis.
Psychical research
An older, more traditional term for parapsychology.
Psychoactive drug
Any substance capable of altering mood, behaviour or conscious mental processes — technically including substances as mild as caffeine, though the term is generally reserved for drugs with more dramatic psychological effects, including hallucinogens and other mind-altering substances, whether used medically or recreationally.
Psychoanalysis
A form of psychotherapy invented and developed by Sigmund Freud, placing central emphasis on uncovering and understanding unconscious motivation. Any later variant of psychoanalysis, however far it has diverged from strict Freudian theory, still shares this core principle. Psychoanalysis is among the most demanding and time-intensive forms of psychotherapy, typically requiring years of frequent sessions, during which powerful underlying conflicts and emotions may surface.
Psychoanalyst
A psychotherapist specifically trained in the theory and clinical techniques of psychoanalysis, typically after first qualifying as a physician, psychiatric social worker or psychologist. A typical psychoanalytic training program lasts around four years and includes the trainee undergoing their own personal analysis.
Psychobabble
A term introduced in the 1970s by writer R. D. Rosen for superficial, pseudo-scientific jargon offered as a quick, simplistic fix for genuine emotional needs or problems — packaged with just enough borrowed psychological terminology to sound credible.
Psychoceramics
A tongue-in-cheek term for the study of eccentric, unfounded or crackpot ideas about human psychology and behaviour.
Psychodiagnostics
Originally referred to attempts to infer personality from external physical features, such as physiognomy or graphology; the term now more commonly encompasses legitimate, well-established projective techniques used in clinical assessment.
Psychodrama
A technique, developed by American psychiatrist Jacob L. Moreno, used in both diagnosis and psychotherapy, in which a person acts out particular scenes from their life, typically in front of other patients and therapists, in order to bring underlying personal and social conflicts into the open. See also: sociometry, another of Moreno's contributions.
Psychodynamics
See dynamic psychology — the study of the underlying motivational forces shaping behaviour.
Psychogalvanic reflex
The American equivalent term for the British galvanic skin response.
Psychohistory
The application of modern psychological theory to the interpretation of historical events and figures. The field is most closely associated, in both popular and academic thinking, with psychobiography — the retrospective psychoanalysis of historical figures, a genre Freud himself helped originate with his study of Leonardo da Vinci. Beyond psychobiography, psychohistorical inquiry has also opened up broader lines of research, including the historical development of psychological concepts themselves (such as mind, insanity, childhood, and the unconscious) and the social psychology of large-scale demographic and attitudinal change over time.
Psychokinesis
In parapsychology, the claimed ability to move physical objects or otherwise influence the physical environment purely through mental effort, without any physical intermediary.
Psycholinguistics
The study of the relationship between the structure, nature and use of language and the underlying psychological processes of the people who use it — spanning language acquisition, comprehension, production and the cognitive representation of language.
Psychological field
See life space — Kurt Lewin's term for the total set of physical and psychological factors shaping a person's behaviour at a given moment.
Psychologist's fallacy
An error in which a psychologist (or observer more generally) mistakenly assumes that their own perspective, motivations or mental state are also present in, or explain, someone else's mind.
Psychology
The scientific study of the mind and behaviour, encompassing how people think, feel, perceive, learn, develop and interact with others, and drawing on methods ranging from controlled laboratory experiments to naturalistic observation and clinical case study.
Psychometrics
The field concerned with the theory and technique of psychological measurement, including the design, validation and scoring of tests and measures of psychological characteristics such as intelligence, aptitude and personality.
Psychomotor
Relating to the influence of mental processes on muscular movement and physical action — as in “psychomotor skills” or “psychomotor retardation.”
Psychopathology
Literally, the pathology of the psyche: the study of psychological disorders, their symptoms, and their underlying causes and development.
Psychophysics
The study of the relationship between physical stimuli from the external world and the subjective sensations and perceptions they produce. These questions remain as central to experimental psychology today as they were when first systematically studied in the earliest psychological laboratories, established in the 1870s. See also: Wundt, Wilhelm.
Psychosis
A severe psychological disorder, disruptive enough to interfere significantly with a person's everyday functioning and sometimes requiring institutional treatment, and generally characterised by a significant loss of contact with shared, consensual reality. While some psychoses have clear organic causes, such as brain damage, others have historically been understood by some psychologists as an extreme form of neurosis; more recent research has increasingly emphasised the role of biochemical factors in at least some forms of psychosis, such as schizophrenia.
Psychosomatic
From the Greek psyche (mind) and soma (body): describing physical disorders in which psychological or emotional stress produces genuine physiological symptoms. Conditions such as certain forms of asthma and stomach ulcers have long been considered at least partly psychosomatic, though some argue that, given the close interconnection of mind and body, virtually every illness has some psychosomatic dimension.
Psychosurgery
Surgery performed on the brain with the specific aim of treating a severe psychological disorder, of which lobotomy is the best-known and now largely abandoned historical example.
Psychotherapist
A person who practises psychotherapy — typically a psychiatrist, clinical psychologist or psychiatric social worker, though in many jurisdictions no specific legal qualification is required to use the title or offer psychotherapy services.
Psychotherapy
The use of psychological, rather than primarily medical, techniques to treat psychological disturbance. The four broad theoretical traditions underlying most forms of psychotherapy are the behaviouristic, cognitive, humanistic and psychoanalytic approaches, with numerous variants, hybrids and integrative approaches developed from these foundations.
Pygmalion effect
See Rosenthal effect — the tendency for a person's performance to improve when others (such as a teacher) hold and communicate higher expectations of them.
Social anthropology
The branch of anthropology concerned with studying social systems, institutions and cultures across different societies, historically with a particular focus on non-literate, small-scale societies.