Hockenbury Discovering Psychology 5th txtbk

196 CHAPTER 5 LearningClassical Conditioning and SurvivalAnimals quickly learn the signals that predictthe approach of a predator. In classicalconditioning terms, they learn to associatethe approach of a predator (the unconditionedstimuli) with particular sounds,smells, or sights (the originally neutralstimuli that become conditioned stimuli).To survive, animals that are vulnerable topredators, such as this frightened deer,must be able to use environmental signalsto predict events in their environment. Arustle in the underbrush, the faint whiff ofa mountain lion, or a glimpse of a humantells the animal that it’s time to flee.According to Rescorla (1988), classical conditioning depends on the informationthe conditioned stimulus provides about the unconditioned stimulus. For learningto occur, the conditioned stimulus must be a reliable signal that predicts the presentationsof the unconditioned stimulus. For the first group of rats, that was certainlythe situation. Every time the tone sounded, a shock followed. But for the secondgroup, the tone was an unreliable signal. Sometimes the tone preceded the shock,and sometimes the shock occurred without warning.Rescorla concluded that the rats in both groups were actively processing informationabout the reliability of the signals they encountered. Rather than merely associatingtwo closely paired stimuli, as Pavlov suggested, the animals assess the predictivevalue of stimuli. Applying this interpretation to classical conditioning, we can concludethat Pavlov’s dogs learned that the bell was a signal that reliably predicted thatfood would follow.According to this view, animals use cognitive processes to draw inferences about thesignals they encounter in their environments. To Rescorla (1988), classical conditioning“is not a stupid process by which the organism willy-nilly forms associations between anytwo stimuli that happen to co-occur.” Rather, his research suggests that “the animal behaveslike a scientist, detecting causal relations among events and using a range of informationabout those events to make the relevant inferences” (Rescorla, 1980).Because of studies by Rescorla and other researchers, today’s understanding of howlearning occurs in classical conditioning is very different from the explanations offeredby Pavlov and Watson (Kirsch & others, 2004). Simply pairing events in time may notbe enough for classical conditioning to occur. Instead, a conditioned stimulus mustreliably signal that the unconditioned stimulus will follow. Put simply, classical conditioningseems to involve learning the relationships between events (Rescorla, 1988).Evolutionary Aspects of Classical ConditioningBiological Predispositions to LearnAccording to Darwin’s theory of evolution by natural selection, both the physicalcharacteristics and the natural behavior patterns of any species have been shaped byevolution to maximize adaptation to the environment. Thus, just as physical characteristicsvary from one species to another, so do natural behavior patterns. Somepsychologists wondered whether an animal’s natural behavior patterns, as shaped byevolution, would also affect how it learned new behaviors, especially behaviors importantto its survival.According to traditional behaviorists, the general principles of learning applied tovirtually all animal species and all learning situations. Thus, they argued that thegeneral learning principles of classical conditioning would be the same regardlessof the species or the response being conditioned. However, in the 1960s, someresearchers began to report “exceptions” to the well-established principles of classicalconditioning (Lockard, 1971; Seligman, 1970). As you’ll see in this section, oneimportant exception involved a phenomenon known as a taste aversion. The studyof taste aversions contributed to a new awareness of the importance of the organism’snatural behavior patterns in classical conditioning.Taste Aversions and Classical Conditioning:Spaghetti? No, Thank You!A few years ago, Sandy made a pot of super spaghetti, with lots of mushrooms, herbs,spices, and some extra-spicy sausage. Being very fond of Sandy’s spaghetti, Don atetwo platefuls. Several hours later, in the middle of the night, Don came down with anasty stomach virus. Predictably, Sandy’s super spaghetti came back up—a colorfulspectacle, to say the least. As a result, Don developed a taste aversion—he avoidedeating spaghetti and felt queasy whenever he smelled spaghetti sauce. Don’s tasteaversion to spaghetti persisted for more than a year.