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Chapter 8 Chapter 8 Presentation Transcript

  • Zeek JonesPSY 428CHAPTER 8 LEARNING THEORY:PAVLOV, WATSON, ANDSKINNER
  • Pavlov• Ivan Petrovich Pavlov(1849–1936)• Physiologist, not apsychologist• Father of modern learningtheory• Won the Nobel Prize for hiswork on the digestivesystem
  • • Restrained a dog in a harness in adark room• Turned on the light• After the light was on for 30seconds, food was given to the dog• This procedure was repeated severaltimes• After a while the light, which initiallyhad no relationship tosalivation, elicited the response byitself. The dog had been conditioned torespond to the light.PAVLOV‘S DOGS
  • • the presentation of food wasan unconditioned stimulus(US); Pavlov did not need to conditionthe animal to salivate to the food.• The light, in contrast, wasa conditioned stimulus (CS); itseffect required conditioning.• Salivation to the food was calledan unconditioned reflex (UR).• salivation to the light was calleda conditioned reflex (CR).• The process itself is called classicalconditioning.
  • • A conditioned stimulus, once established, does not continue to work forever. Pavlovfound that even though he could make a light a CS for salivation, if he flashed the lightalone over several trials, it began to lose its effect. Drops of saliva became fewer andfewer until there were none at all. At this point, Extinction had occurred• Although a reflex has been conditioned to only one stimulus, it is not just that particularstimulus that elicits it. The response seems to generalize over a range of similar stimuliwithout any further conditioning, this is called Stimulus Generalization• Initial generalization gradually gives way to a process of differentiation. If one continuesto ring bells of different tones (without presenting food), the dog begins to respond moreselectively, restricting its responses to the tones that most closely resemble the originalCS. One can also actively produce differentiation by pairing one tone with food whilepresenting another tone without food. This would be called an experiment in stimulusDiscrimination• Pavlov showed, finally, that once he had solidly conditioned a dog to a CS, he could thenuse the CS alone to establish a connection to yet another neutral stimulus. In oneexperiment, Pavlov‘s student trained a dog to salivate to a bell and then paired the bellalone with a black square. After a number of trials, the black square alone producedsalivation. This is called Second-order/Higer-oreder Conditioning. Pavlov found thatin some cases he could also establish third-order conditioning, but he could not gobeyond this point.OTHER PRINCIPLES OF CONDITIONING
  • • John Broadus Watson (1878–1958)• Most responsible for making Pavlovianprinciples a part of the psychologicalmainstream• In 1913 Watson made a great impact onpsychology by issuing amanifesto, ―Psychology as theBehaviorist Views It.‖ In this article heargued that the study of consciousnessthrough introspection has no place inpsychology as a science• In 1916, Watson began research onyoung children, becoming the first majorpsychologist to apply principles oflearning to the problems of developmentWATSON
  • • One of Watson‘s major interests was the conditioning of emotions. He claimed that at birth there are only threeunlearned emotional reactions—fear, rage, and love.• Fear, Watson said, is observed when infants suddenly jump or start, breathe rapidly, clutch their hands, closetheir eyes, fall, and cry. There are only two unconditioned stimuli that elicit fear. One is a sudden noise; theother is loss of support (as when the baby‘s head is dropped). Yet older children are afraid of all kinds ofthings—strange people, rats, dogs, the dark, and so on. Therefore it must be that the stimuli evoking mostfear reactions are learned. For example, a little boy is afraid of snakes because he was frightened by a loudscream when he saw one. The snake became a conditioned stimulus.• Rage is initially an unlearned response to the restriction of body movement. If we grab a 2-year-oldgirl, preventing her from going where she wants, she begins to scream and stiffens her body. She lies downstiff as a rod in the middle of the street and yells until she becomes blue in the face. Although rage is initially areaction to one situation—being forcibly held—it later is expressed in a variety of situations; children becomeangry when told to wash their faces, sit on the toilet, get undressed, take a bath, and so on. Such commandselicit rage because they have been associated with physical restraint in these situations. The child becomesangry when told to get undressed because this order was initially associated with being forcibly held.• Love is initially a response that is automatically elicited by the stroking of the skin, tickling, gentle rocking, andpatting. The baby responds by smiling, laughing, gurgling and cooing, and other responses that we callaffectionate, good natured, and kindly. Although Watson had no use for Freud, he noted that such responses―are especially easy to bring about by the stimulation of what, for lack of a better term, we may call theerogenous zones, such as the nipples, the lips, and the sex organs‖.STUDY OF EMOTIONS
  • • Watson wanted to see if he could condition Albert to fear awhite rat. At the beginning of the experiment Albertshowed no such fear. Next, the experimenter on fouroccasions presented the rat and simultaneously pounded abar behind Albert‘s head, producing a startle response. Onthe fifth trial Albert was shown the rat alone, and hepuckered his face, whimpered, and withdrew. He had beenconditioned to fear the rat. For good measure, theexperimenter combined the rat and the pounding twicemore, and on the next trial, when the rat was againpresented alone, Albert cried and tried to crawl away asrapidly as he could.• A few days later, Watson and Raynor tested for stimulusgeneralization. They found that although Albert playedwith many objects, he feared anything furry. He cried orfretted whenever he saw a rabbit, dog, fur coat, cottonwool, or a Santa Claus mask, even though he previouslyhad not been afraid of these things. Albert‘s fear hadgeneralized to all furry objects.• One of Watson‘s major practical innovations was a methodfor deconditioning fears. He was not able to deconditionAlbert of his new fears, because Albert was an orphan whowas adopted and taken out of town before this could beattempted. But Watson advised one of hiscolleagues, Mary Cover Jones, on procedures foreliminating the fears of another little boy, a 3-year-oldcalled Peter.LITTLE ALBERT
  • • Peter seemed active and healthy in every respect exceptfor his fears. He was scared of white rats, rabbits, furcoats, feathers, cotton wool, frogs, fish, and mechanicaltoys. As Watson noted, ―One might well think that Peterwas merely Albert B. grown up, but Peter was a differentchild whose fears were ‗home grown‘‖• Peter was placed in his highchair and given amidafternoon snack. Then a caged white rabbit wasdisplayed at a distance that did not disturb him. The nextday, the rabbit was brought increasingly closer, until heshowed a slight disturbance. That ended the day‘streatment. The same thing was done day after day; therabbit was brought closer and closer, with theexperimenter taking care never to disturb Peter very much.Finally, Peter was able to eat with one hand while playingwith the rabbit with the other. By similar means, Joneseliminated most of Peter‘s other fears as well.• Jones‘s technique, although anticipated by Locke, wasquite innovative at the time. It is today known as a formof behavior modification called systematicdesensitization. The subject is relaxed and graduallyintroduced to the feared stimulus. The experimenter makessure that the subject is at no time made to feel tooanxious. Gradually, then, the subject learns to associaterelaxed feelings, rather than fear, to the object or situation.LITTLE PETER
  • • Burrhus Frederic "B. F." Skinner (1905–1990)• Like Watson, Skinner was a strict behaviorist. Hebelieved psychology should dispense with anyreferences to intangible mental states (such asgoals, desires, or purposes); instead, it shouldconfine itself to the study of overt behavior• In contrast to Watson, however, Skinner‘s primarymodel of conditioning was not Pavlovian. Theresponses that Pavlov studied, Skinner said, arebest thought of as respondents. These areresponses that are automatically ―elicited‖ byknown stimuli. For example, the ingestion of foodautomatically elicits salivation, and a loud noiseautomatically elicits a startle response. Mostrespondents are probably simple reflexes.• Skinner was interested in operant behavior. Inoperant behavior, the animal is not harnessedin, like Pavlov‘s dogs, but moves freely about and―operates‖ on the environmentSKINNER
  • • To study operant conditioning, Skinnerconstructed an apparatus that is commonlyreferred to as a ―Skinner box.‖ This is a fairlysmall box in which an animal is free to roamabout. At one end there is a bar (lever)that, when pressed, automatically releaseswater or a pellet of food.• The animal, such as a rat, at first pokesaround until she eventually presses thebar, and then she gets the reward.• As time goes on, she presses the bar morefrequently. The most important measure oflearning, for Skinner, is the rate of responding;when responses are reinforced, their rates ofoccurrence increase.• In Skinner‘s apparatus, the bar presses areautomatically registered on a graph, so theexperimenter need not be present much of thetime. The data are presented as a learningcurveSKINNER BOX
  • • Skinnerians have performed numerous experiments showing that human behavior, beginning in infancy, can becontrolled by reinforcing stimuli. For example, infants increase their rates of sucking when sucking results insweet, as opposed to nonsweet, liquid. Similarly, infants‘ rates of smiling and vocalization can be increased if thebehavior leads to rewards such as the experimenter‘s smiles, caresses, and attention• In such experiments, one is dealing with different kinds of reinforcers. Some reinforcers, such as food or the removalof pain, are primary reinforcers; they have ―natural‖ reinforcing properties. Other reinforcing stimuli, such as an adult‘ssmiles, praise, or attention, are probably conditioned reinforcers; their effectiveness stems from their frequentassociation with primary reinforcers• Operant behavior, like respondent behavior, is also subject to extinction. For example, because children do things―just to get attention‖, one can extinguish undesirable behaviors, such as excessive crying or temper tantrums, byconsistently withdrawing one‘s attention whenever they occur• Operant behavior that has apparently been extinguished may also show spontaneous recovery. For example, a littleboy whose temper tantrums had been extinguished through the withdrawal of attention began having tantrums onceagain when placed in a new situation The behavior had to be extinguished further.• Skinner found he could initially establish responses at the highest rates when he reinforced them promptly. A rat willbegin pressing a bar at a high rate only if she has promptly received a food pellet each time she has done so. thisprinciple has importance for child rearing. If a father shows pleasure immediately after his son brings him thenewspaper, the boy is likely to repeat the behavior the next evening. If, however, the father is so engrossed insomething else that he delays reinforcing his son‘s behavior for a few minutes, the boy‘s behavior will not bestrengthened. In fact, what gets strengthened is the boy‘s behavior at the moment of reinforcement. If he is buildingblocks at that moment, it is block-building, not newspaperfetching, that gets reinforced.PRINCIPLES OF CONDITIONING
  • • In operant conditioning, as in respondent conditioning, there is a process of stimulusgeneralization. Suppose a little girl has been reinforced for saying ―Da da‖ at the sight of herfather, but not when she is looking at her mother or siblings. The father has become adiscriminative stimulus. It is not unusual, however, to find the girl saying ―Da da‖ when shesees any man at all, such as strangers on the street. The stimulus has generalized. Her parentsmust now teach her to make a finer discrimination. They might say, ―That‘s right,‖ when sheutters ―Da da‖ in the presence of her father, but not when she looks at any other man.• Operant behavior is not acquired in all-or-nothing packages. It is usually learned gradually, littleby little. When we teach a boy to swing a baseball bat, we first say ―Good‖ when he gets hishands into the right grip. We then say ―Right‖ when he lifts his bat in the correct position over hisshoulder. We then work on his stance, a level swing, and so on—gradually shaping thecomplete behavior.• Reinforcement means strengthening a response (increasing its rate), and positivereinforcements strengthen responses by adding positive consequences such as food, praise, orattention. Responses may also be strengthened through negative reinforcement, by removingunpleasant or aversive stimuli. When we punish, in contrast, we do not try to strengthenbehavior but to eliminate it.• Punishment, however, does not always work. In an early experiment, Skinner found that whenhe punished rats for bar pressing (by having the bar swing back and smack them on thelegs), he only temporarily suppressed the response. In the long run, punishment did noteliminate the response any faster than did extinction. Other studies have obtained similarresults, and the findings conform to everyday experience. Parents who hit their children get themto behave for a while, but the parents find that the misconduct reappears later on.
  • • unconditioned stimulus• conditioned stimulus• unconditioned reflex• conditioned reflex• classical conditioning• extinction• Stimulus Generalization• Discrimination• Second-order/Higer-orederConditioning• systematic desensitization• operant behavior• Reinforcing• spontaneous recovery• discriminative stimulus• Shaping• negative reinforcementKEY TERMS