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 pigs • 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 Avoidance Escape CS CS US US R R Shuttle Box • Standard experimental paradigm Escape • • • • In presence of 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, qualify 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 processes 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 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 – No 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 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 more shocks, strengthening CR again and increasing avoidance response • But… we don’t 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 • 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 Reduction 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 • Giving 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 avoidance 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: 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 punishment – 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 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 FR-3 punishment light response-independent punishment Yoked Suppression ratio Phase 2: tone light tone Trials Delay • Interval 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 Cumulative responses no punishment FR 1000 FR 500 FR 100 FR 5 Time 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-reinforcement pauses Alternative Sources of Reinforcement • Options • Availability of reinforceable alternatives increases suppression of punished response no punishment Punishment, no alternative response available Cumulative responses – No alternatives but punished behaviour – Alternative behaviours (e.g., differential reinforcement schedules; DRA, DRI, etc.) Punishment, alternative response available Time 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 • Punisher 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 explicit 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 weakening 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