Kimberly Price, age 15, of Harrisburg, Pa., for her question:
WHAT EXACTLY IS INSTINCT?
Instinct is behavior that is inherited rather than learned. We use the terms "instinct" and "instinctive behavior" only for activity that involves neither experience nor learning.
To be truly instinctive, a behavior trait must be typical of almost all members of at least one sex or a species of animal.
All animals perform both instinctive actions and learned actions. Instinct almost completely determines the behavior of insects, spiders and crustaceans such as crabs and lobsters. These animals can learn only a little, and so their survival depends on built in behavior patterns.
Higher animals, including fish, birds and mammals, can learn. They also modify their instinctive behavior by learning. The higher the animal, the more it can learn and the less it depends on instinct. Fish behave more by instinct than do birds, and birds perform more instinctive actions than do mammals.
Among humans, babies smile and suck instinctively. But as humans grow older, most of their acts are learned.
Most instinctive behavior is released or brought about by a stimulus. It is something that makes the animal act as it does.
Blinking at a bright light is a type of unlearned behavior released by a stimulus, but it is a reflex rather than an action caused by instinct.
Reflex actions, such as pulling back your hand from a hot pan handle, are less complicated than instinctive behavior.
Survival for animals higher than insects depends on a combination of instinct, learning and body changes.
In many cases, a releasing stimulus acts on one or more glands in an animal's body. For example, seasonal changes in the amount of daylight affects the glands of some kinds of birds.
The glands secrete fluids called hormones. A change in the amount of hormones secreted stimulates the birds to migrate.
If a gland does not secrete a certain hormone properly, it is then possible that an animal may not be able to carry out the instinctive behavior associated with that hormone.
Some glands produce hormones only at a certain stage in an animal's life. The sex glands, as an example, do not function completely in young animals.
Another type of behavior pattern is called "imprinting." It occurs when an animal learns to recognize a stimulus that will later release instinctive behavior.