Operant Learning Theory

The earliest studies of operant learning can be traced back to the research of psychologist E. L. Thorndike with cats in puzzle boxes (Kimble, 1961). In Thorndike's experiments, hungry cats had to escape from boxes fastened shut in different ways to obtain food. Thorndike observed that after being placed in the boxes, the cats engaged in various behaviors such as pacing, visually exploring, and scratching at the walls. The animals perfomled these responses until they accidentally pressed the latch, pulled the string, or did something else that opened the box. On successive trials, the cats spent more time examining and scratching at the latch or the string, while the other responses gradually dropped out. Finally. the animal would perform the correct behavior as soon as it was placed in the box. Thorndike explained the learning of this new behavior with his "law of effect": In situations where responses are followed by events that give satisfaction, those responses become associated with and are more likely to recur in that situation. B. F. Skinner. another American psychologist, greatly refined the experimental apparatus that permitted the study and conceptualization of operant learning. The "Skinner Box," a chamber with a lever that could be programmed to deliver food following lever presses, provided several improvements over Thorndike's puzzle boxes. One advantage was that the relationship between lever presses and food delivery was arbitrary and could be readily manipulated by the experimenter. This allowed for the study of a wide range of variables, such as the ratio of responses to food deliveries, the time interval between responses that would produce food. and variations in stimuli that signaled the previous and other contingencies. A second advantage of Skinner's apparatus was that it permitted the use of response rate as a measure of response strength or response probability. Response rate is a continuous variable that can fluctuate over time, and it is more sensitive to subtle valiations in environmental conditions than latency until escape (i.e., from a puzzle box), or duration of maze-running, or other early measures of leaming. A third advantage of the operant chamber and its measure of response rate was that it allowed the study of histories of reinforcement and other variables that affect leamed behavior, such as those influencing extinction and maintenance (Skinner, 1966). Skinner drew an important distinction between operant behavior, which operated on the environment to change it and which was affected by stimuli that followed it, and respondent behavior, an earlier discovered form of learning. Respondent behavior, elucidated by the Russian physiologist Ivan P. Pavlov, involved reflexive responses (e.g., salivation, eye