Hockenbury Discovering Psychology 5th txtbk

200 CHAPTER 5 LearningThe investigation of how voluntary behaviors are acquired began with a youngAmerican psychology student named Edward L. Thorndike. A few years beforePavlov began his extensive studies of classical conditioning, Thorndike was usingcats, chicks, and dogs to investigate how voluntary behaviors are acquired.Thorndike’s pioneering studies helped set the stage for the later work of anotherAmerican psychologist named B. F. Skinner. It was Skinner who developed operantconditioning, another form of conditioning that explains how we acquire and maintainvoluntary behaviors.Edward Lee Thorndike (1874–1949) As agraduate student, Thorndike became fascinatedby psychology after taking a classtaught by William James at Harvard University.Interested in the study of animal behavior,Thorndike conducted his first experimentswith baby chicks. When his landladyprotested about the chickens in his room,Thorndike moved his experiments, chicksand all, to the cellar of William James’shome—much to the delight of the Jameschildren. Following these initialexperiments, Thorndike constructed hisfamous “puzzle boxes” to study learningin cats. Later in life, Thorndike focused hisattention on improving educational materials.Among his contributions was theThorndike Barnhart Student Dictionaryfor children, which is still published today(R. L. Thorndike, 1991).Thorndike’s Puzzle Box Shown here is oneof Thorndike’s puzzle boxes, which weremade mostly out of wood slats and wiremesh. Thorndike constructed a total of 15different puzzle boxes, which varied in howdifficult they were for a cat to escape from.In a simple box like this one, a cat merelyhad to pull on a loop of string at the backof the cage to escape. More complex boxesrequired the cat to perform a chain ofthree responses—step on a treadle, pull ona string, and push a bar up or down(Chance, 1999).Thorndike and the Law of EffectEdward L. Thorndike was the first psychologist to systematically investigate animallearning and how voluntary behaviors are influenced by their consequences. Atthe time, Thorndike was only in his early 20s and a psychology graduate student.He conducted his pioneering studies to complete his dissertation and earn his doctoratein psychology. Published in 1898, Thorndike’s dissertation, titled Animal Intelligence:An Experimental Study of the Associative Processes in Animals, is the mostfamous dissertation ever published in psychology (Chance, 1999). When Pavlovlater learned of Thorndike’s studies, he expressed admiration and creditedThorndike with having started objective animal research well before his own studiesof classical conditioning (Hearst, 1999).Thorndike’s dissertation focused on the issue of whether animals, like humans,use reasoning to solve problems (Dewsbury, 1998). In an important series of experiments,Thorndike (1898) put hungry cats in specially constructed cages that hecalled “puzzle boxes.” A cat could escape the cage by a simple act, such as pullinga loop or pressing a lever that would unlatch the cage door. A plate of food wasplaced just outside the cage, where the hungry cat could see and smell it.Thorndike found that when the cat was first put into the puzzle box, it wouldengage in many different, seemingly random behaviors to escape. For example, thecat would scratch at the cage door, claw at the ceiling, and try to squeeze throughthe wooden slats (not to mention complain at the top of its lungs). Eventually, however,the cat would accidentally pull on the loop or step on the lever, opening thedoor latch and escaping the box. After several trials in the same puzzle box, a catcould get the cage door open very quickly.Thorndike (1898) concluded that the cats did not display any humanlike insightor reasoning in unlatching the puzzle box door. Instead, he explained the cats’learning as a process of trial and error (Chance, 1999). The cats gradually learnedto associate certain responses with successfully escaping the box and gaining thefood reward. According to Thorndike, these successful behaviors became “stampedin,” so that a cat was more likely to repeat these behaviors when placed in the puzzlebox again. Unsuccessful behaviors were gradually eliminated.Thorndike’s observations led him to formulate the law of effect: Responses followedby a “satisfying state of affairs” are “strengthened” and more likely to occuragain in the same situation. Conversely, responses followed by anunpleasant or “annoying state of affairs” are “weakened” and lesslikely to occur again.Thorndike’s description of the law of effect was an importantfirst step in understanding how active, voluntary behaviors canbe modified by their consequences. Thorndike, however, neverdeveloped his ideas on learning into a formal model or system(Hearst, 1999). Instead, he applied his findings to education,publishing many books on educational psychology (Beatty,1998). Some 30 years after Thorndike’s famous puzzle-boxstudies, the task of further investigating how voluntary behaviorsare acquired and maintained would be taken up by anotherAmerican psychologist, B. F. Skinner.