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Lecture

PS261 - Chapter 3 Textbook.docx

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Department
Psychology
Course
PS261
Professor
Bruce Mc Kay
Semester
Winter

Description
Intro to Learning – Chapter 3  Classical conditioning enables human and nonhuman animals to take advantage of the orderly sequence of events in environment to take appropriate actions in anticipation of what is about to happen The Early Years of Classical Conditioning  Classical conditioning began by Pavlov  Also independently discovered by Edwin Twitmyer submitted in 1902 o Repeatedly tested knee-jerk response by sounding a bell 0.5 seconds before hitting knee o Bell was sufficient to elicit the knee-jerk reflex  Pavlov’s research was extension of research on process of digestion o Made major advances in study of digestion by developing stomach fistulae that collects various digestive juices o Secretions could be used to study the mechanisms of association learning and functions of the nervous system The Discoveries of Vul-fson and Snarskii  First systematic studies of classical conditioning performed by Vul-fson and Snarskii in Pavlov’s laboratory o Focused on salivary glands  After dogs were exposed to food in the mouth enough times, the sight of the drugs was enough to make them salivate  Substances produce distinctive texture and taste sensations in the mouth o Orosensory stimuli o Dog learns to associated visual feature of substance with its orosensory features o Object learning – association of one feature of an object with another  To study associative learning – stimuli have to be manipulated independently of one another Classical Conditioning Paradigm  Pavlov’s basic study involved two stimuli o Tone or light o Food or sour solution  Conditioned Stimulus – tone or light  Conditioned response – salivation that was elicited by the light  Unconditioned stimulus – the food substances  Unconditional response – salivation elicited by food Experimental Situations  Fear conditioning  Watson and Rayner investigated the conditioning of emotional reactions o Assumed there was a simple method by means of which range of stimuli which can induce emotions  Conditioned fear response in Albert to the presence of a white lab rat  Presenting rat to Albert and then associating that with the sound of a metal bar being hit by a hammer o After 2 – Albert did not want to touch the rat o By 7 – showed strong fear response  Conditioned fear generalized to all furry things  Fear and anxiety sources of considerable human discomfort and can lead to serious psychological and behavioural problems  Rats show their fear by freezing, animals that aren’t moving are not easily seen by predators o Immobility of body and absence of movement of whiskers  Conditioned suppression - suppression of ongoing behaviour  Two more measures of immobility - lick-suppression procedure o Animals are slightly water deprived and lick readily when put into an experimental chamber with a drinking spout o If fear CS presented, licking behaviour is suppressed and takes longer to make specified number of licks  Conditioned emotional response o Rats first trained to press response lever for food reward o Lever press provides behavioural baseline for fear measurement o Once rats are pressing at a steady rate, fear conditioning is introduced  Tone or light paired with a brief shock  To measure suppression of lever pressing, suppression ratio is calculated o Compares number of lever presses that occur during the CS with number that occur during a comparable baseline period before CS is presented o Suppression ratio of zero if rat suppresses lever pressing during CS  Suppression Ratio = CS responding CS responding + pre – CS responding  Example: if rat presses lever 30 times pre-CS and 30 times after CS, then suppression ratio will be 0.5 0.5 = 30   30+30  No suppression on first day, but gradual suppression as CS was exposed to rats  Smaller the suppression ratio, the more motionless the animal Eyeblink Conditioning  Eye blink reflex early component of startle response and occurs in many species  Eye blink conditioning extensively investigated in studies with human participants early in development of learning theory o Provides tool for studying problems in development, aging & Alzheimers o Used extensively in studies of neurobiology of learning  Ivkovich et al.  Eye-blink conditioning in five month old infants  Found increased response to CS in group where CS was paired with US compared to when CS paired with US randomly  Important points about learning: *** o Showed that classical conditioning requires pairing of CS to US o Responding to CS did not develop in the unpaired control group o Learning was not observable at first  Also conducted on domesticated rabbits o Rabbits rarely blink, ideal for eye-blink research o Rabbit eye blink conditioning relatively slow, requires several hundred trials for substantial levels of conditioned responses Sign Tracking  Moving toward and possibly contact with stimulus that signals the availability of a positive reinforcement  Tend to approach contact stimuli that signal availability of food o Availability of food can be predicted by some key aspects, such as its appearance at a distance  Investigated in lab by presenting discrete visual stimulus just before each delivery of a small amount of food  Brown and Jenkins  Pigeons placed in experimental chamber that had illuminated circular key that illuminated so pigeons could peck o Illuminated for 8 seconds before food was delivered  Started pecking the light hoping to get food - Not required to gain access to food  Presenting key light at random or unpaired with food does not lead to pecking  Tracking of signals for food dramatically illustrated by instances when signal far from food source o Pigeons - went to key light when CS was presented before approaching the food o Quails - Birds approached CS before approaching location of female (8 ft)  CS elicited strong enough appeal that it attracted male quails more than the female  Only occurs in situations where Cs is localized and can be approached and tracked Learning What Tastes Good and What Tastes Bad  Taste aversion theory o Learned if ingestion of a novel flavour followed by an aversive consequence such as indigestion or food poisoning  Taste preference theory o May be learned if followed by nutritional repletion or other positive consequence  Human taste aversions result of Pavlovian conditioning - typically involves
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