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PSY319H5 (17)


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University of Toronto Mississauga

Chapter 5: Learning and Behaviour Habituation: ● we react automatically to events: ● orienting response – organism directs appropriate sensory organ toward source of novel stimulus ● habituation – simplest form of learning: learning not to respond to an unimportant event that occurs repeatedly ● George Humphrey – experiment with snails, got used to tapping so wouldnt retreat into shell ● from evolutionary perspective – waste of time and energy ● Wicks and Rankin – used worm Nemoda and subjected them to taps or heat  found that this withdrawing effect occurs through neurons that respond to mechanical stimulus, regardless of stimulus  could produce habituation to tap-elicited stimulus but not to heat – shows they learned something about tap and could distinguish it from reaction to source of heat  only had 302 neurons in NS ● short term habituation – simplest form ● long term habituation – animals with more complex nervous system ● pattern of experience plays a role in distinguishing long-term and short-term:  when sitmuli are massed into quick repetitions, habituation is rapid but ST  when sitmuli are presented in small groups that are spaced over time, habituation is slower but LT  evidence that 2 different neural mechanisms are responsible for this Classical Conditioning: ● invovled learning about conditions that predict that a significant event will occur ● Pavlov – noticed dogs salivated when they saw research assistant come into room so he set up experiment with bell and food and dogs learned to salivate when they heard bell ring ● Classical Conditioning – process by which a response normally elicitied by one stimulus (UCS) comes to be controlled by another stimulus (CS) as well ● sequence and timing is important ● unconditional stimulus – stimulus that naturally elicits a reflexive response ● unconditional response - behaviour itself that is naturally elicited by UCS ● conditional stimulus – stimulus that, because of repeated association with UCS, eventually elicits conditional response ● conditional response – response elicited by CR Biological Significance of Classical Conditioning: ● two funcitons:  ability to learn to recognize stimuli that predicts occurence of an important event allows learner to make appropriate response faster and more effectively ■ siamese fighting fish more likely to win fight if they were given stimulus (CS) that intruding male (UCS) would enter territory ■ blue gouramis more likely to mate sooner and produce more offspring when they received stimulus (CS) signalling approaching female (UCS) ■ learning that occurs with biologically significant UCS is more resistant to subsequent modifications  stimuli that were previously unimportant acquire some properties of important stimuli with which they have been associated and thus become able to modify behaviour ■ neutral stimulus becomes desirable when it is associated with desirable stimulus or becomes undesirable when it is associated with undesirable stimulus ■ specific properties of UCS become associated with CS - UCS takes on symbolic value ■ Ward-Robinson – demonstrated this with pigeons where they pecked at light when sound went on (paired sound CS with food UCS) ● adaptive significance is so general that even nematode exhibits it ● Wen – placed worms in solution of Na+ or Cl- with bacteria; when placed with patches on ions and no bacteria, worm migrated to ions thinking there was food Basic Principles of Classical Conditioning: ● discovered 7 interesting phenomena: acquisition, extinction, spontaneous recovery, stimulus generalization, and discrimination Acquisition: ● acquisition – time during wich CR appears and increases in frequency ● strength of CR is influenced by: intesity of UCS and timing of CS and UCS  more intense UCS produces rapid learning  more intense UCS stronger the CR is  classical conditioning occurs fastest when CS occurs shorlty before UCS and both end at same time  0.5 seconds is optimal delay between onset of CS and UCS  little conditioning if CS follows UCS, or if too long or short delay will be slower and weaker Extinction and Spontaneous Recovery: ● extinction – elimination of a response that occurs when CS is repeatedly presented without being followed by UCS  participant learns that CS is no longer followed by UCS – if neither are presented then extinction doesn't occur  doesn't necessarily disappear permanently ● spontaneous recovery – after an interval of time, reappearance of response that had previously extinguished Stimulus Generalization and Discrimination: ● generalization – CR elicited by stimuli that resembles CS used in training  once response has been conditioned to CS similar stimuli will also elicit that response  more stimuli resembles CS more likely it will elicit CR ● discrimination – appearance of CR when one stimulus is presented (CR+) but not another one (CR-) accomplished by using 2 CS during training – one is followed by the UCS and another isn't  involes learning difference between 2 or more stimuli Conditioned Emotional Responses: ● many stimuli are able to arouse emotional response (disgust, contempt, fear, anger, sadness, tenderness, longing, or sexual desire) ● many had no special signifance but were paired with stimuli that elicited strong emotional reaction so they acquired emotional or evaluative signifance ● Todrank, Byrnes, Wrzesniewski, and Rozin – people associated pleasant or unpleasant odour with attractive or unactriveness of person in photograph ● phobias – unreasonable fear of specific onjects or situations learned through classical learning  at some time early in life person was exposed to now-fearsome object in conjunction with stimulus that elicited pain or fear  classical conditioning can occur without direct experience with CS or UCS – can be learned through observation (vicariously)  imaginary episodes that we picture as we hear or read story (UCS) can provide imaginary stimuli (CS) that lead to real conditional emotional responses (CR)  therapists use knowledge of principles of learning to eliminate them  suggestions that biologically relevant stimuli are especially prone to classically conditioned emotional responses What is learned in Classical Conditioning: ● research shows that for classical conditioning to occur, CS must be reliable predictor of UCS ● neutral stimulus becomes a CS only when following conditions are satisfied:  CS regularly occurs prior to presentation of UCS  CS does not regularly occur when UCS is absent ● principle has been clearly established by conditioning phenomenon known as blocking ● blocking – prevention of or attenuation in learning that occurs to a neutral CS when it is conditioned in presence of a previously conditioned stimulus  CSA is paired with UCS, then new CSB is presented together with CSA and compound of 2 stimuli is followed by UCS; compared to condition where CSA has not been previously trained, CSB acquires little, if any, CR  UCS is also predicted by CSA so CSB brings no new information about UCS – would only provide new information if the UCS changed at same time CSB was introduced ● classical conditionig provides two types of information: what and when of future events  what: ■ allows animals to learn that particular event is about to occur ■ behaviour is determined by memory of event ■ Hilliard and Domjan – examined conditioning of sexual behaviours in male Japanese quail ● showed that male birds block of grey foam (CS) and then allowed birds to interact with female bird (UCS) for 5 minutes; after several such pairings males showed large increase in time they interacted with CS object ● behaviour to CS was determined by males memory of UCS ● males were then given access to 8 birds for 40 minutes (satiated condition) and others were given no access (deprived condition) ● when birds were later shown CS, satiated males gave less sexual responses ● implies that what was learned involved memory of UCS – memory that could be altered by subsequent experience such as satiation  when: ■ if CS follows UCS, animal could learn that CS predict absence of UCS for long period of time ■ if backward conditioning occurs, animals show inhibitory conditional response as contrasted with excitatory conditional response ● inhibitory conditional response – reponse tendency conditioned to signal that predicts absence of UCS; generally not observed directly but assessed through other tests ● excitatory conditional response – response tendency conditioned to signal that UCS is about to occur; type of CR exemplified Pavlov's salivation response ■ learn something about timing of events during conditioning trial ■ Cole and Miller – trained rats in conditioned procedure in which backward CSB followed UCS ● after substantial training, UCS was eliminated and a forward CSF was presented just before CSB ● speculated that form of temporal integration would occur ● even though CSF had never been presented prior to UCS, rats behaved as though it signalled upcoming UCS ● it associated the UCS and the CSB with the CSF Operant Conditioning: ● operant conditioning – form of learning in which behaviour is affected by its consequences; favourable consequences strengthen behaviour and unfavourable consequences weaken behaviour  relations between environmental stimuli and our own behaviour (operant – organism learn through responding, through operating on environment) The Law of Effect: ● Edward Thorndike set up lab with cat in William James's basement  taught cat to open latch of box to get food  called “learning by trial and accidental success”  cat learned to make correct responses only because they were followed by favourable outcome ● law of effect – consequences of behaviour determine whether it is likely to be repeated  like natural selection in sense that it determines which behaviours will survive ● Skinner – selection of consequences: ability to adjust behaviour to fit changes in environment is highly adaptive ● behaviour analysis – understanding behaviour-environmental interactions Skinner and Operant Behaviour: ● Skinner – advocated study of law of effect and applications of behaviour analysis and its methods to solving human problems ● devised objective methods for studying behaviour, invented apparatus and methods for observing it, and created own philosophy for interpreting it ● wrote several books, and novel Walden Two that showed how we could use it to better society ● operant chamber – apparatus devised in which animal's behaviour can be easily observed, manipulated, and automatically recorded  provides unconstrained opportunity for simple response to be performed by animal ● behaviour analysts manipulate environmental events to determine their effect on response rate (number of responses emitted during given amount of time) ● events that increase response rate are said to strengthen responding and events that decrease response rate are said to weaken responding ● cumulative recorder – mechanical device connected to opperant chamber for purpose of recording operant responses as they occur in time (measures response rate) ● better than Thorndike:  participants can emit responses more freely over greater period of time  participants can be studied for longer periods of time without interferce produced by researcher handling or otherwise interacting with them between trials Three-Term Contingency: ● discriminative stimulus – stimulus that sets occasion for responding because, in past, behaviour produced certain consequences in presence of that stimulus  say word “speak” and give dog food when he barks ● three-term contingency – relation among discriminative stimuli, behaviour, and consequences of that behaviour; a motivated organism emits specific response in presence of discriminative stimulus because, in past, that response has been reinforced only when disrcriminative stimulus is present  discriminative stimulus sets occasion for response which produces favourable consequence  favourable consequence strengthen relationships between discriminative stimulus and response ● distinguished in following way:  preceding event (discriminative stimulus) sets occasion for responing because, in past wehn stimulus occured, response was followed by certain coonsequences  response we make is called operant behaviour  following event is consequence for operant behaviour ● consequences are contingent on behaviour ● once operant behaviour is established, it occurs every time discrminative stimulus occurs, even if other aspects of environment change Reinforcement, Punishment and Extinction: ● operant behaviour can be followed by five different kinds of consequences: positive reinforcement, negative reinforcement, punishment, response cost, and extinction Positive reinforcement: ● positive reinforcement – increase in frequency of response that is regularly and reliably rewarded by an appetitive stimulus  positive reinforcer - appetitive stimulus that follows response and icnreases frequency of response ● negative reinforcement – increase in frequency of response that is regularly and reliably followed by termination of aversive stimulus  negative reinforcer - aversive stimulus that is terminated as soon as response occurs and thus increases frequency of that response ● punishment – decrease in frequency of response that is regularly and reliably followed by an aversive stimulus  punisher – aversive stimulus that follows a response and decreases frequency of that response  several negative side effects: ■ unrestrained use of physical force may cause serious bodily harm ■ punishment often induces fear, hostility, and other undesirable emotions in people receiving punishment – may result in retaliation against punisher ■ through punishment, organisms learn only which responses not to make – punishment does not teach organism desirable behaviour ● response cost – decrease in frequency of a response that is regularly and reliably followed by termination of an appetitive stimulis  form of punishment  time out of positive reinforcement (omission) – procedure that produces response cost when it is used to remove a person physically from an activity that is reinforcing to that person  punishment causes behaviour to decrease whereas negative reinforcement causes behaviour to increase ● extinction – decrease in frequency of previously reinforced response because it is no longer followed by a reinforcer  different from forgetting – when behaviour is not rehearsed (or memory not thought about for a long time) Other Operant Procedures and Phenomena: Shaping: ● shaping – reinforcement of behaviour that successively approximates desired response until that response is fully acquired  to begin, one must be able to recognize target behaviour  changing criteria in training an animal to perform complex behaviour Intermittent Reinforcement: ● intermittent reinforcement – occassional reinforcement of particular behaviour; produces responding that is more resistant to extinction  follows 2 patterns:  each response has certain probability of being reinforced ■ probability-based patterns ■ require a variable number of responses for each reinforcer ■ number of responses is related to reinforcer (more responses = more reinforcement) ■ ratio schedule of reinforcement – apparatus controlling operant chamber may be programmed to deliver reinforcer after a certain number of responses ■ if ratio is constant, animal will respond rapidly, receive reinforcer, pause a little while, and then begin responding again ● called fixed-ratio schedule – schedule of reinforcement in which reinforcement occurs only after fixed number of responses have been made since previous reinforcement (or start of session) ■ if ratio is variable, averaging a particular number of responses but varying from trial to trial, animal will respond at steady, rapid pace ● called variable-ratio schedule – schedule of reinforcement similar to fixed-ratio schedule but characterized by variable response requirement having a particular mean  responses are reinforced after particular intervals of time have elapsed ■ response is reinforced only after particular time interval has elapsed ■ interval schedule of reinforcement – after various intervals of time, a response will be reinforced ■ if time intervals are fixed, animal will stop responding after each reinforcement – learns that responses made immediately after each reinforcement are never reinforced ● called fixed-interval schedule – schedule of reinforcement in whcih first response that is made after fixed interval of time since previous reinforcement (or start of session) is reinforced ■ if time intervals are variable, animal will respond at slow, steady rate – that way it will not waste time and energy on useless responses but won't miss opportunities for reinforcement either ● called variable-interval schedule – schedule of reinforcement similar to fixed-interval schedule but characterized by variable time
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