Instinct

We use the term instinct to describe species-typical behavior that is seemingly performed without aid of prior experience, but what we seem to mean is that the animal moves and behaves as if mysterious and unknown forces were guiding it. Many people who study animal behavior argue that the term instinct is not ultimately helpful because it tells us little about the real mechanisms underlying behavior. The use of the term indicates only that the behavior is relatively closed to modification by experience—nothing more. Since nervous system tissues are soft, delicate, and often very complex, understanding the operation of these structures in producing behavior presents a great challenge. This, combined with the role of experience in producing many superficially "instinctive" behaviors, makes things even more difficult.

Many behaviors held up as examples of instinct are shown to have an experiential component: for instance, as new gull chicks continue to peck at bill-like objects, the accuracy of their pecking improves and the kinds of bill-like objects they will peck at are increasingly restricted. Thus, the wide variety of behavioral patterns observed in living organisms surely represents a continuum, from those not much influenced by learning to those that are greatly influenced by it; a strict "nature versus nurture" dichotomy is probably too simplistic to describe any animal behavior.

The answer to the question "Under what conditions should a behavior be genetically closed, and when should a provision be made for learning?" seems to be related to the situation's predictability in nature. When it is crucial that the correct response to some occurrence be carried out the first time (like a kangaroo rat faced with a striking rattlesnake), natural selection should favor a fairly rigid, infallible program to underlie an appropriate response. The existence of a reliable relationship between some environmental cue and a biologically appropriate response permits the development of a releaser for triggering the "right" reaction the first time, whether to a predator, potential mates, or one's own offspring.