PSY402 Theories of LearningThe Role of Environmental StimuliDefinitions of TermsGeneralization GradientKinds of GradientsSlide Number 6DiscriminationThe sharpness of the generalization gradient depends on the type of trainingFlat GradientsGeneralization of InhibitionExcitatory and Inhibitory Generalization with Line Tilt StimuliExplanationDiscrimination LearningTwo-Choice Discrimination TasksCategorization and DiscriminationTest Slides – Tree CategoryTest Slides – Water CategoryTest Slides -- Margaret CategoryMore Complex TasksApparatus (Part 1)Examples of positive imagesExamples of positive imagesThree PhasesConditional DiscriminationBehavioral ContrastAnticipatory ContrastOccasion SettingSD as an Occasion SetterConclusionsPeak ShiftHypothetical Excitatory and Inhibitory gradientsHypothetical Excitatory and Inhibitory GradientsPeak ShiftErrorless Discrimination LearningImplications of Errorless TrainingApplication of Errorless TrainingIs Learning Relational?Mackintosh’s Attentional View8.17 Examples of computer stimuli presented to pigeons by Cook (Part 1)8.17 Examples of computer stimuli presented to pigeons by Cook (Part 2)8.17 Examples of computer stimuli presented to pigeons by Cook (Part 3)8.18 “Same” and “different” displays used in the experiment by Wasserman et alContinuity TheoryPSY402Theories of LearningChapter 10 – Stimulus Control of BehaviorThe Role of Environmental Stimuli{ In operant conditioning, the stimulus becomes associated with the reinforcer or punishment.z Reward or punishment is the UCS.z The stimulus signaling reward or punishment is the CS.{ The CR motivates operant behavior.z Responding can be used as a measure of the strength of a CR.Definitions of Terms{ Stimulus 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 Gradient{ Degrees of generalization occur.z In some situations, the same response occurs to similar stimuli.z In other situations, the amount of response varies with the similarity.{ Generalization gradient –a graph showing how the strength of response changes with similarity.z Steep gradients mean narrow response (stimuli must be very similar).Kinds of Gradients{ Excitatory conditioning (S+) – a CS-UCS response to a stimulus is learned.z 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.z Inhibitory gradient – the S- is varied and the CR is measured.redgreenyellow-orangeorange-redyellowyellow-greenDiscrimination{ The shape of the gradient can be changed by training.{ When birds are exposed to two different tones (S+or S-), they must discriminate between them.z Responding is less generalized because the competing tone produces no reward.z The shape of the gradient becomes steeper and more narrow at the top.The sharpness of the generalization gradient depends on the type of trainingFlat Gradients{ A 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 Inhibition{ Inhibition example: fear of dating.z 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.Excitatory and Inhibitory Generalization with Line Tilt StimuliExplanation{ Lashley-Wade theory – people and animals generalize because they are unable to discriminate.z Can’t tell the difference between stimuliz A contrast is needed during training to enable discrimination.{ Discrimination training leads to steeper generalization gradients.{ Perceptual experience matters.Discrimination Learning{ Important to recognize when reinforcement is not available so that responding can be withheld.{ Discriminative stimulus:z SD– reinforcement is available (S+)z SΔ– reinforcement is unavailable (S-){ Conditioned stimuli always produce a response. Discriminative stimuli signal the opportunity to respond.Two-Choice Discrimination Tasks{ The discriminative stimuli are on the same dimension:z Red vs green light.{ Need not be presented simultaneously.{ Two-choice discrimination includes one SDand one SΔ .{ Other tasks can use multiple multiple SD or multiple SΔ.Categorization and Discrimination{ Animals respond to stimuli in ways that suggest they form categories.z Pigeons can classify a variety of items, including new images not seen before.z The items to be learned as members of a category are SDand signal opportunity for food.z The items that are not members of the category are SΔand signal that pecking will not be rewarded.Test Slides – Tree CategoryTest Slides – Water CategoryTest Slides -- Margaret CategoryMore Complex Tasks{ Later pigeons were asked to place images into four categories by pressing one of four buttons (rewarded by food if correct).z They are “naming” the object shown.{ Pigeons do equally well with natural and manufactured objects (cars, chairs).{ Transfer to new stimuli is worse but above chance.Apparatus (Part 1)Examples of positive imagesExamples of positive imagesThree Phases{ Subjects begin by responding equally to both stimuli –prediscrimination phase.{ Discrimination phase -- with training, response to SDincreases and response to SΔdeclines.{ Shift back to non-differential reinforcement to show that behavior was caused by reinforcement.Conditional Discrimination{ Availability of reinforcement depends on the condition of a stimulus.z The stimulus does not always signal the same thing.{ More difficult to learn.{ Nissen’s chimpanzees:z Large, small squares, white or black.z SD= large white, small black.Behavioral Contrast{ Behavioral contrast – the increased responding to the differential stimulus, decreased response to SΔ{ Contrast also occurs with changes in the duration of reinforcement.z VI-10 to VI-3{ Local contrast –emotional { Sustained contrast – related to the differential reinforcement.Anticipatory Contrast{ Williams – sustained contrast occurs due to anticipation of a future reinforcement contingency.z Not due to recall of past contingency.{ VI-3, VI-6, VI-3z Compare the first and third VI-3 behavior.z VI-6 affected the first VI-3 more than the last VI-3 -- a
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