Instinct

Instinct or innate behavior is the inherent inclination of a living organism toward a particular behavior.

The simplest example of an instinctive behavior is a fixed action pattern, in which a very short to medium length sequence of actions, without variation, are carried out in response to a clearly defined stimulus.

Any behavior is instinctive if it is performed without being based upon prior experience (that is, in the absence of learning), and is therefore an expression of innate biological factors. Sea turtles, newly hatched on a beach, will automatically move toward the ocean. A joey climbs into its mother's pouch upon being born. Honeybees communicate by dancing in the direction of a food source without formal instruction. Other examples include animal fighting, animal courtship behavior, internal escape functions, and the building of nests. All of these are examples of complex behaviors and are thus substantially different from simple reflex behaviors.

An instinct should be distinguished from a reflex, which is a simple response of an organism to a specific stimulus, such as the contraction of the pupil in response to bright light or the spasmodic movement of the lower leg when the knee is tapped. Instincts, in contrast, are inborn complex patterns of behavior that must exist in every member of the species and that cannot be overcome by force of will. However, the absence of volitional capacity must not be confused with an inability to modify fixed action patterns. For example, people may be able to modify a stimulated fixed action pattern by consciously recognizing the point of its activation and simply stop doing it, whereas animals without a sufficiently strong volitional capacity may not be able to disengage from their fixed action patterns, once activated.

Commonly cited examples of presumed instincts in humans are the "maternal instinct" and the "survival instinct". These examples however do not conform to the scientific definition of instinct. Many human females do not desire children and furthermore some mothers kill their own children. Similarly, many humans contradict their own survival through suicide.

The role of instincts in determining the behavior of animals varies from species to species. The more complex the neural system of an animal, the greater is the role of the cerebral cortex, and social learning and instincts play a lesser role. A comparison between a crocodile and an elephant illustrates how mammals for example are heavily dependent on social learning. Lionesses and chimpanzees raised in zoos away from their birth mothers most often reject their own offspring because they have not been taught the skills of mothering. Such is not the case with simpler species such as reptiles.