student
C H A P T E R
5
LEARNING
kowa_c05_162-194hr.indd 162
9/13/10 11:03 AM
A
n experiment by John Garcia and his colleagues adds a new twist to all the stories ever told about wolves and sheep. The researchers fed a wolf a muttonburger (made of the finest sheep flesh) laced with odorless, tasteless capsules of lithium chloride, a chemical that induces nausea. Displaying a natural preference for mutton, the animal wolfed it down but half an hour later became sick and vomited (Garcia & Garcia y Robertson, 1985; Gustavson et al., 1976).
Several days later, the researchers introduced a sheep into the wolf’s compound. At the sight of one of its favorite delicacies, the wolf went straight for the sheep’s throat. But on contact, the wolf abruptly drew back. It slowly circled the sheep. Soon it attacked from another angle, going for the hamstring. This attack was as short lived as the first. After an hour in the compound together, the wolf still had not attacked the sheep—in fact, the sheep had made a few short charges at the wolf!
Lithium chloride seems to have been the real wolf in sheep’s clothing.
Although the effects of a single dose of a toxic chemical do not last forever, Garcia’s research illustrates the powerful impact of learning. In humans, as in other animals, learning is central to adaptation. Knowing how to distinguish edible from inedible foods, or friends from enemies or predators, is essential for survival. The range of possible foods or threats is simply too great to be prewired into the brain. Learning is essentially about predicting the future from past experience and using these predictions to guide behavior.
For example, even the simplest organisms respond to the environment with reflexes. A reflex is a behavior that is elicited automatically by an environmental stimulus, such as the knee-jerk reflex elicited by a doctor’s rubber hammer. (A stimulus is something in the environment that elicits a response.) In perhaps
5
LEARNING
kowa_c05_162-194hr.indd 162
9/13/10 11:03 AM
A
n experiment by John Garcia and his colleagues adds a new twist to all the stories ever told about wolves and sheep. The researchers fed a wolf a muttonburger (made of the finest sheep flesh) laced with odorless, tasteless capsules of lithium chloride, a chemical that induces nausea. Displaying a natural preference for mutton, the animal wolfed it down but half an hour later became sick and vomited (Garcia & Garcia y Robertson, 1985; Gustavson et al., 1976).
Several days later, the researchers introduced a sheep into the wolf’s compound. At the sight of one of its favorite delicacies, the wolf went straight for the sheep’s throat. But on contact, the wolf abruptly drew back. It slowly circled the sheep. Soon it attacked from another angle, going for the hamstring. This attack was as short lived as the first. After an hour in the compound together, the wolf still had not attacked the sheep—in fact, the sheep had made a few short charges at the wolf!
Lithium chloride seems to have been the real wolf in sheep’s clothing.
Although the effects of a single dose of a toxic chemical do not last forever, Garcia’s research illustrates the powerful impact of learning. In humans, as in other animals, learning is central to adaptation. Knowing how to distinguish edible from inedible foods, or friends from enemies or predators, is essential for survival. The range of possible foods or threats is simply too great to be prewired into the brain. Learning is essentially about predicting the future from past experience and using these predictions to guide behavior.
For example, even the simplest organisms respond to the environment with reflexes. A reflex is a behavior that is elicited automatically by an environmental stimulus, such as the knee-jerk reflex elicited by a doctor’s rubber hammer. (A stimulus is something in the environment that elicits a response.) In perhaps