PSY402 Theories of LearningStimulus GeneralizationThe Role of Environmental StimuliDefinitions of TermsGeneralization GradientKinds of GradientsShapes of GradientsFlat GradientsGeneralization of InhibitionExplanationPSY402Theories of LearningWednesdayFebruary 19, 2003Stimulus GeneralizationChapter 7The Role of Environmental StimuliIn operant conditioning, the stimulus becomes associated with the reinforcer or punishment.Reward or punishment is the UCS.The stimulus signaling reward or punishment is the CS.The CR motivates operant behavior.Responding can be used as a measure of the strength of a CR.Definitions of TermsStimulus control -- Environmental stimuli signal the opportunity for reward or punishment. Generalization – responding in the same way to similar stimuli.Discrimination – responding to some stimuli but not to others.Generalization GradientDegrees of generalization occur.In some situations, the same response occurs to similar stimuli.In other situations, the amount of response varies with the similarity.Generalization gradient – a graph showing how the strength of response changes with similarity.Steep gradients mean narrow response (stimuli must be very similar).Kinds of GradientsExcitatory conditioning (S+) – a CS-UCS response to a stimulus is learned.Excitatory gradient – the S+ is varied and the CR is measured.Inhibitory conditioning (S-) – a CS signals absence of the UCS and thus inhibits the CR.Inhibitory gradient – the S- is varied and the CR is measured.Shapes of GradientsMost sensory stimuli produce similar gradients.Pigeons pecking at colored lights.Tones paired with shocks.Words paired with pretzels or candy:Synonyms and homonyms produce salivation.Semantic similarity works best.Flat GradientsA flat gradient means all stimuli are being responded to as if they were the same.Responding with a gradient to a tone occurred only when the tone signaled reward during training.Generalization of InhibitionInhibition example: fear of dating.A good experience leads to less fear of dating a different person.Inhibition gradients are similar to excitatory gradients – the more the stimulus varies, the less inhibition.ExplanationLashley-Wade theory – people and animals generalize because they are unable to discriminate.Can’t tell the difference between stimuliA contrast is needed during training to enable discrimination.Discrimination training leads to steeper generalization gradients.Perceptual experience
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