Hockenbury Discovering Psychology 5th txtbk

188 CHAPTER 5 LearningClassical Conditioning in Early Life:White Coats and Doctor Visits Most infantsreceive several vaccinations in their firstfew years of life. The painful injection(a UCS) elicits fear and distress (a UCR).After a few office visits, the clinic, nurse,or even the medical staff’s white lab coatscan become a conditioned stimulus (CS)that elicits fear and distress—even in theabsence of a painful injection.Factors That Affect ConditioningOver the three decades that Pavlov (1928) spent studying classical conditioning,he discovered many factors that could affect the strength of theconditioned response (Bitterman, 2006). For example, he discovered thatthe more frequently the conditioned stimulus and the unconditionedstimulus were paired, the stronger was the association between the two.Pavlov also discovered that the timing of stimulus presentations affectedthe strength of the conditioned response. He found that conditioning wasmost effective when the conditioned stimulus was presented immediately beforethe unconditioned stimulus. In his early studies, Pavlov found that ahalf-second was the optimal time interval between the onset of the conditionedstimulus and the beginning of the unconditioned stimulus. Later,Pavlov and other researchers found that the optimal time interval could varyin different conditioning situations but was rarely more than a few seconds.Stimulus Generalization and DiscriminationPavlov (1927) noticed that once a dog was conditioned to salivate to a particularstimulus, new stimuli that were similar to the original conditioned stimulus couldalso elicit the conditioned salivary response. For example, Pavlov conditioned a dogto salivate to a low-pitched tone. When he sounded a slightly higher-pitched tone,the conditioned salivary response would also be elicited. Pavlov called this phenomenonstimulus generalization. Stimulus generalization occurs when stimuli that aresimilar to the original conditioned stimulus also elicit the conditioned response,even though they have never been paired with the unconditioned stimulus.Just as a dog can learn to respond to similar stimuli, so it can learn the opposite—to distinguish between similar stimuli. For example, Pavlov repeatedly gave a dogsome food following a high-pitched tone but did not give the dog any food followinga low-pitched tone. The dog learned to distinguish between the two tones, salivatingto the high-pitched tone but not to the low-pitched tone. This phenomenon,stimulus discrimination, occurs when a particular conditioned response is made toone stimulus but not to other, similar stimuli.Higher Order ConditioningIn further studies of his classical conditioning procedure, Pavlov (1927) found thata conditioned stimulus could itself function as an unconditioned stimulus in a newconditioning trial. This phenomenon is called higher order conditioning or secondorderconditioning. Pavlov paired a ticking metronome with food until the sound ofthe ticking metronome became established as a conditioned stimulus. Then Pavlovrepeatedly paired a new unconditioned stimulus, a black square, with the tickingmetronome—but no food. After several pairings, would the black square alone producesalivation? It did, even though the black square had never been directly pairedwith food. The black square had become a new conditioned stimulus, simply bybeing repeatedly paired with the first conditioned stimulus: the ticking metronome.Like the first conditioned stimulus, the black square produced the conditioned response:salivation.It is important to note that in higher order conditioning,the new conditioned stimulus has never been paired with theunconditioned stimulus. The new conditioned stimulus acquiresits ability to produce the conditioned response byvirtue of being paired with the first conditioned stimulus(Gewirtz & Davis, 2000; Jara & others, 2006).Consider this example: Like most children, our daughterLaura received several rounds of immunizations when she was aninfant. Each painful injection (the UCS) elicited distress andmade her cry (the UCR). After only the second vaccination, Lauradeveloped a strong classically conditioned response—just thesight of a nurse’s white uniform (the CS) triggered an emotional