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Chapter 10

Intro to Learning - Chapter 10

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Wilfrid Laurier University
Anneke Olthof

Learning – Chapter 10  Avoidance procedure – make specific response to prevent aversive stimulus  Punishment – positive contingency, response produces aversive outcome  Avoidance Behaviour o Origins of the study of avoidance behaviour  Investigations originated in studies of classical conditioning  First experiment conducted by Bechterev o Interested in studying associative learning  1930s  Classical conditioning procedure and procedure that had instrumental avoidance component added  Studies conducted proved that avoidance conditioning is different from standard classical conditioning o The discriminated avoidance procedure  Investigators concerned with importance of warning signal in avoidance procedures and relation of warning to US and instrumental response  Discriminated/signaled/avoidance method  Involves discrete trials, initiated by warning stimulus o If subject makes target response before shock is delivered, CS turned off  Avoidance trial o If subject fails, scheduled shock appears until response occurs  Escape trial  Shuttle avoidance  When animals shuttles back and forth between two compartments to avoid aversive stimuli  Two-way avoidance – moves in different directions on successive trial  One-way avoidance – starts trial on same side and always moves in the same direction, to other side  One-way avoidance is easier to learn o Two-process theory of avoidance  Avoidance procedures involve negative contingency  Absence of aversive stimulus the reason that avoidance responses are made  Mowrer and Lamoreaux 1942  Not getting something can hardly qualify as rewarding  Two-process theory of avoidance  Dominant theoretical viewpoint on avoidance learning for many years  No longer viewed as complete explanation of avoidance learning  Standard which other explanations are measured against  Two mechanisms involved o Classical conditioning process activated by pairings of warning stimulus with aversive event on trials when organism fails to make avoidance response  Classical conditioning of fear to the CS o Learning instrumental avoidance response occurs because response terminates CS and reduces conditioned fear elicited by CS  Instrumental reinforcement of the avoidance response through fear reduction  Both mechanisms depend on each other o Instrumental response is not possible until fear is conditioned to the CS  Explains avoidance behaviour in terms of escape from conditioned fear rather than prevention of shock o Experimental analysis of avoidance behaviour Brian Kwok 1 Learning – Chapter 10  Avoidance learning subject of numerous experiments  Acquired-drive experiments  In typical avoidance procedure, classical conditioning of fear, instrumental reinforcement through fear reduction occur intermixed throughout trials  Goal of acquired-drive experiment o If they make separate contributions to avoidance learning  Possible to demonstrate their operation in situation where two types are not intermixed  Basic strategy first to condition fear to CS with pure classical conditioning procedure which CS is paired with US regardless of what subject does o Next phase – subjects periodically exposed to fear-eliciting CS and allowed to perform instrumental response to turn off CS  Called this because drive to perform instrumental response learned through classical conditioning rather than being innate  Escape from fear paradigm (FFE) o FFE upheld predictions of two-process theory o Termination of conditioned aversive stimulus effective reinforcer for instrumental behaviour  Independent measurements of fear during acquisition of Avoidance Behaviour  Approach based on assumption that if fear motivates and reinforces, then conditioning of avoidance behaviour should go hand in hand o Conditioned fear and avoidance responding not always highly correlated  Less fearful if they become proficient at performing avoidance response o Dissociation between fear and avoidance learning observed in human subjects  Successful avoidance behaviour associated with low fear levels and low expectations of danger  Decline in fear to CS with extended training presents puzzle to two-process theory  Extinction of avoidance behaviour through response-blocking and CS-alone exposure  If avoidance response effective in terminating CS, avoidance responding can persist for a long time  How do you terminate avoidance behaviour? o Flooding / response prevention  Presenting CS in avoidance situation without US, subject can’t perform avoidance response  Implosive therapy  Two important components  Exposure to CS without aversive stimulus  Blocking access to avoidance response  Procedures in which avoidance response is blocked, permit return of fear and make fear more accessible to extinction  Response blocking makes it clear that failure to make avoidance response no longer results in aversive stimulus and facilitates readjustment of previously acquired expectancies  Nondiscriminated (Free-Operant) Avoidance  Avoidance conditioning that has no warning signal  Aversive stimulus to occur without warning, if avoidance response is made, period of safety o Repetition of the avoidance response serves to start safe period again  Two time intervals Brian Kwok 2 Learning – Chapter 10 o S-S interval (Shock-shock)  Interval between shocks in absence of response o R-S interval (Response-shock)  Period of safety created by each response  Avoidance response can occur at any time and will reset the R-S interval  Demonstrations of Free-Operant Avoidance Learning  Avoidance learning conducted with animals and humans o Tested with more “natural aversive stimuli  Lejuez et al 1998 o College students and exposure to carbon dioxide was the aversive stimulus  CO2 produces symptoms related to panic attacks  Rate of responding controlled by length of the S-S and R-S intervals o More frequently shocks scheduled in absence of responding (S-S), more likely subject to learn the avoidance respondce o Increasing periods of safety produced by the response (R-S) promotes avoidance behaviour  Safe period must be longer than interval between shocks  Free-Operant Avoidance and Two-Process Theory  Free-operant provide no clear explanation on how avoidance response reduces fear  Intervals remain fixed during experiment , so animals can learn to respond to passage of time as signal  Temporal conditioning permits application of mechanisms of two-process theory to free-operant avoidance procedures o Temporal cues can become conditioned to elicit fear  Response effectively removes fear-eliciting temporal cues because each avoidance response restarts intervals o Temporal cues have same role as explicit CS in discriminative avoidance  Predictions show that responses will be near the R-S interval because this is where greatest amount of fear is elicited  Avoidance behaviour successfully conditioned where S-S and R-S intervals varied throughout experiment o Making it unpredictable makes it difficult to use time as a cue o Alternative theoretical accounts of avoidance behaviour  Reinforcement for avoidance behaviour assumed to be provided by fear reduction  Negative reinforcement – reinforcement due to removal of aversive stimulus  Positive reinforcement through conditioned inhibition of fear or conditioned safety signals  Safety signals o Feedback stimuli that acquires conditioned inhibitory properties and become signals for absence of aversive stimulation  Safety-signal hypothesis o Safety signals that accompany avoidance responses may provide positive reinforcement for avoidance behaviour o Introducing explicit feedback stimulus facilitates learning of avoidance response  Spatial, tactile, proprioceptive stimuli that accompany avoidance response becomes safety signal o Can be modified to provide explicit safety signal  Safety-signal hypothesis well suited to explain free-operant avoidance behaviour Brian Kwok 3 Learning – Chapter 10  Response-associated feedback cues can come to provide positive reinforcement for free-operant avoidance response  Reinforcement of avoidance through reduction of shock frequency  Shock-frequency reduction o Proposed as alternative to two-process theory o Avoidance responses prevent shock delivery, reducing frequency of shocks o Hypothesis views reduction of shocks to be critical to reinforcement of avoidance behaviour o Sidman 1962– first to claim shock-frequency reduction as cause of avoidance behaviour  Many not necessary for avoidance learning, but may be contributing factor  Avoidance and species-specific defense Reactions (SSDRs)  Before fear reduction can be effective reinforcer, fear must be conditioned to CS o Before response feedback cues can come to serve as reinforcer, must become signal for absence of shock  Before shock-frequency reduction can work, organisms must experience enough socks to calculate shock frequencies  For avoidance mechanism to be useful under natural conditions, has to generate successful avoidance responses quickly o Avoidance mechanism that requires numerous training trials is no use  Species-specific defense reactions o Innate responses assumed to have evolved because they are successful in defense against pain and injury  Major prediction of SSDR theories that some responses more easily learned in avoidance experiments than others  Predatory imminence and defensive and recuperative behaviours  Focusing on ecological and evolutionary influences on defensive behaviour advanced thinking about fear and avoidance learning  Predatory imminence continuum (Fanselow and associates) o Different defensive responses occur depending on level of danger faced by animal o Different species typical defense responses assumed to occur at different levels of predatory imminence  Assumes defensive behaviour initially occurs as unconditioned responding o Can also be come to be elicited by conditioned stimulus if CS becomes associated with aversive event  If CS precedes US, defensive behaviour one level lower on predatory-imminence scale than response elicited by US  If US elicits circa strike response, CS elicits freezing behaviour  If CS and US presented at the same time, defensive response more similar to US response  Differences in behavioural manifestiations of different degrees of predatory imminence associated with corresponding cascade of neurobiological states o Evolution created powerful/specialized behavioural/neurobiological processes  Does not include instrumental conditioning component, not intended to explain diverse array of experimental findings o Important to consider in all aversive conditioning situations  Can also be used to characterize human fear and anxiety reactions
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