Instinct, a complex unlearned (inborn) response to a stimulus or group of stimuli. Instinctive behavior and reflex action are often difficult to distinguish. A true reflex is a simple, unlearned activity such as swallowing, sucking, and grasping. An instinct is a complicated unlearned combination of reflexes—the flying of birds, for example. A habit, on the other hand, is a learned form of behavior that becomes largely automatic through repetition.
In animals below the human level, instinctive responses include mating, parental behavior, ways of securing food, and swimming or other methods of locomotion. Until early in the 20th century, psychologists considered human behavior to include various instincts such as maternal, acquisitive, and pugnacious. Since then, experiments have shown less evidence of the existence of instincts in humans, and more evidence pointing to the importance of learned behavior.
Today psychologists generally consider instincts to be peculiar to the lower animals, and avoid the term “instinctive” with regard to human behavior. Many maintain that anything a person does that is not reflex action is something that has been learned.
Even in the lower animals it is often difficult to tell how much of the behavior is inborn and how much is modified by learning. For example, each bird of a species tends to build nests in the same way as others of its species. However, the nest pattern and the materials for building can be adapted to the location in which the nest is made.
