One of the most widespread and important types of learning is
which involves increasing a behavior by following it with a reward, or decreasing a
behavior by following it with punishment. For example, if a mother starts giving a boy
his favorite snack every day that he cleans up his room, before long the boy may spend
some time each day cleaning his room in anticipation of the snack. In this example, the
boy’s room-cleaning behavior increases because it is followed by a reward or
Unlike classical conditioning, in which the conditioned and unconditioned stimuli are
presented regardless of what the learner does, operant conditioning requires action on the
part of the learner. The boy in the above example will not get his snack unless he first
cleans up his room. The term
refers to the fact that the learner must
or perform a certain behavior, before receiving a reward or punishment.
Thorndike’s Law of Effect
Some of the earliest scientific research on operant conditioning was conducted by
American psychologist Edward L. Thorndike at the end of the 19th century. Thorndike’s
research subjects included cats, dogs, and chickens. To see how animals learn new
behaviors, Thorndike used a small chamber that he called a puzzle box. He would place
an animal in the puzzle box, and if it performed the correct response (such as pulling a
rope, pressing a lever, or stepping on a platform), the door would swing open and the
animal would be rewarded with some food located just outside the cage. The first time an
animal entered the puzzle box, it usually took a long time to make the response required
to open the door. Eventually, however, it would make the appropriate response by
accident and receive its reward: escape and food. As Thorndike placed the same animal
in the puzzle box again and again, it would make the correct response more and more
quickly. Soon it would take the animal just a few seconds to earn its reward.
Based on these experiments, Thorndike developed a principle he called the
law of effect.
This law states that behaviors that are followed by pleasant consequences will be
strengthened, and will be more likely to occur in the future. Conversely, behaviors that
are followed by unpleasant consequences will be weakened, and will be less likely to be
repeated in the future. Thorndike’s law of effect is another way of describing what
modern psychologists now call operant conditioning.
Thorndike was studying mind reading in children for his PhD. He asked children to guess
what he was thinking and if they guessed right, he rewarded them with a piece of candy.
What he observed was that children made the same guesses again when it led to a piece