1、Aversive Control: Avoidance and Punishment,Avoidance/Escape,Escape: getting away from an aversive stimulus in progress Avoidance: preventing the delivery of an aversive stimulus Negative contingency between response and aversive stimulus Increase in operant responding,Brogden et al. (1938),Guinea pi
2、gs CS = tone, US = shock, UR = pain, CR = running Classical conditioning group CS followed by US Avoidance group CS - CR no US CS - no CR US,Discriminative Avoidance,Stimulus signals onset of aversive US,CS,US,R,CS,US,R,Avoidance,Escape,Shuttle Box,Standard experimental paradigm,Escape,In presence o
3、f aversive stimulus Make response Aversive terminated Negative reinforcement,Avoidance “Paradox”,Make response before aversive delivered Behaviour clearly increases, so reinforcer But what is taken away (or delivered)? Mowrer & Lamoreaux (1942) “not getting something can hardly, in and of itself, qu
4、alify as rewarding.”,Two-Process Theory,Two mechanisms: classical and instrumental 1. Classical conditioning process activated by CS when avoidance not made; CR of fear produced 2. Negative reinforcement: successful avoidance removes fear caused by CS Classical and instrumental conditioning processe
5、s are independent Avoidance = escape from fear, not prevention of shock,Acquired Drive Experiment,Phase 1: condition fear to CS through classical conditioning procedure Phase 2: let subject make operant response to terminate CS No shock Drive to avoid learned through classical conditioning,Brown and
6、 Jacobs (1949),Rats in shuttle box Experimental and control groups Phase 1: light/tone CS shock Phase 2: CS no shock; turn CS off by crossing barrier Measure: time to change sides Supports two-process theory Termination of fear CS drives operant response,Rescorla & LoLordo (1965),Dog in shuttlebox N
7、o signal Response gives “safe time” Pair tone with shock Tone increases rate of response CS+ can amplify avoidance CS- can reduce avoidance,Problems for Theory,Fear a necessary component Fear reduction with experience,Kamin, Brimer & Black (1963),Rats Lever press in operant chamber for food Auditory
8、 CS+ for shock; avoidance in shuttle box until: 1, 3, 9, 27 avoidances in a row CS+ in operant chamber; check for suppression of lever press,Alternation of Behaviour (Yo-yo),Every successful avoidance puts CS on extinction With extinction, fear drops, so motivation to avoid decreases Resulting in mo
9、re shocks, strengthening CR again and increasing avoidance response But we dont really see this,Persistence of Avoidance,Sometimes a problem Phobias Need to extinguish avoidance Flooding, response prevention,Sidman Free-Operant,Can avoidance be learned without warning CS? Shocks at random intervals
10、Response gives safe time Extensive training, but rats learn avoidance (errors, high variability across subjects),Hernstein & Hineline (1966),Rapid and slow shock rate schedules Response switches from rapid to slow Shift back to rapid random so no time signal Response produces shock reduction,Reducti
11、on of Shock Frequency,Molar account Response reduces in amount of shocks over long run Negative reinforcement Overall shocks taken away, behaviour increases,Safety Signals,Molecular account Positive reinforcement Context cues associated with “safety” Either SD or CS- Making response gives safety Giv
12、ing explicit stimuli makes avoidance learning easier,SSDRs,Species-specific defense reactions Innate responses; evolved SSDRs predominate in initial stages of avoidance Hierarchy If first SSDR works, keep it If not, try next, etc. Aversive outcome (punishment) is the selector of appropriate avoidanc
13、e response,SSDRs,Fight, flight, freeze Also thigmotaxis, defensive burying, light avoidance, etc. Environmental content influences selected SSDR E.g., freezing not useful if predator right in front of you Some responses easier to learn than others E.g., rats: wheel run avoid shock (easy) E.g., rats:
14、 rear avoid shock (hard),Predatory Imminence,Different innate defensive behaviours at different danger levels,Differences from SSDR,1. Behaviours in anticipation, not response 2. Predatory imminence, not environmental cues leads to response 3. Not selected via punishment,Punishment,Positive punishme
15、nt Delivery of stimulus reduction in behaviour Negative punishment Removal of stimulus reduction in behaviour Time out Overcorrection,Introduction of Punisher,Effective use of punishment Tolerance Start with high(er) intensity Can then reduce and behaviour will remain suppressed,Response-Contingent
16、vs. Response-Independent,Does your response cause the aversive outcome? More behavioural suppression if aversive stimulus produced by operant response,Phase 1: train on VI-60 sec,Phase 2: tone lightFR-3 response-independentpunishmentpunishment Yoked,tone,light,Suppression ratio,Trials,Delay,Interval
17、 between response and delivery of aversive Longer the delay, less suppression of behaviour,Punishment Schedule,Continuous or intermittent schedules Azrin (1963) Different FR punishment schedules; responding maintained with VI reinforcement,no punishment,FR 1000,FR 500,FR 100,FR 5,Time,Cumulative res
18、ponses,Positive Reinforcement Schedules and Punishment,Without some positive reinforcement, behaviour generally stops quickly As in previous study, responding maintained with appetitive outcome on VI schedule Interval Overall decrease VI: suppressed but stable FI: scalloping Ratio Increases post-rei
19、nforcement pauses,Alternative Sources of Reinforcement,Options No alternatives but punished behaviour Alternative behaviours (e.g., differential reinforcement schedules; DRA, DRI, etc.) Availability of reinforceable alternatives increases suppression of punished response,no punishment,Punishment, no
20、 alternative response available,Punishment, alternative response available,Time,Cumulative responses,SD for Punishment,Suppression limited to presence of SD E.g., garden owl E.g., cardboard “cops” and “kids”,Punishment as SD for Availability of Pos. Reinf.,Sometimes punishment seeking behaviour Puni
21、sher becomes S+ for positive reinforcement E.g., masochism, children seeking attention,CER Theory of Punishment,Estes (1944) Conditioned suppression E.g., freeze prevents lever press CER incompatible with making response Punishment suppresses behaviour through same mechanism In real world, no explic
22、it CS Stimuli immediately before punished response serve this function Estes (1969): incompatible motivational state,Avoidance Theory of Punishment,Tied to two-process theory Engage in incompatible behaivour Prevents making punished behaviour Strengthening of competing avoidance response Not weakeni
23、ng of punished response Same theoretical problems of avoidance,Negative Law of Effect,Thorndike (1911) Positive reinforcement and punishment are symmetrical opposites Similar to Premack Principle Low probability behaviours reduce high probability behaviours Forced to engage in low-valued behaviour after doing high probability behaviour,
