A concept introduced by Nikolaas Tinbergen, a European pioneer of ETHOLOGY. His observations of stickleback fish led him to wonder how male sticklebacks, who never saw a female until they were sexually mature, knew to chase away certain sticklebacks (i.e. males) and to woo others (i.e. females). The fish were reacting to the presence of red colouring on the male’s belly or its absence on the female’s. This was the mechanism that released their INNATE response.
