Chapter 7

Reinforcement Schedules

• Cumulative recorder
• No response: flat line
• Response: slope
• Cumulative record

(Figure 1)

The Accumulation of the Cumulative Record

(Figure 2)

Fixed Ratio (FR)

• N responses required; e.g., FR 25
• CRF = FR1
• Rise-and-run
• Postreinforcement pause
• Steady, rapid rate of response
• Ration strain

(Figure 3)

Variable Ratio (VR)

• Varies around mean number of responses; e.g., VR 25
• Rapid, steady rate of response
• Short, if any postreinforcement pause
• Longer schedule --> longer pause
• Never know which response will be reinforced

(Figure 4)

Fixed Interval (FI)

• Depends on time; e.g., FI 25
• Postreinforcement pause
• Scalloping
• Time estimation
• Clock doesn’t start until reinforcer given

(Figure 5)

Variable Interval (VI)

• Varies around mean time; e.g., VI 25
• Steady, moderate response rate
• Don’t know when time has elapsed
• Clock doesn’t start until reinforcer given

(Figure 6)

Response Rates

(Figures 7 and 8)

Extinction of Reinforcement

• Variable harder to extinguish than fixed
• Partial reinforcement effect
• Discrimination hypothesis
• Random element
• Generalized decrement hypothesis
• Similarity of schedule to extinction

(Figure 9)

Other Reinforcement Schedules

• Differential reinforcement of high rates (DRH)
• Reinforcement only if more than X responses in a set time
• Differential reinforcement of low rates (DRL)
• Reinforcement only if less than X responses in a set time

Concurrent Schedules

• Two (or more) response choices at once
• Multiple levers/keys
• Choice

Chained Schedules

• Sequential responses
• Signaled by discriminative stimuli

(Figure 10)

Factors Affecting Performance

• Reinforcement schedule
• Reinforcer quality and/or amount
• Delay for reinforer delivery
• Response effort
• Motivation
• Previous reinforcement history

"Why I work with bugs…"

• Human/animal differences
• Contingency-shaped
• Three-term contingency
• Based on reinforcement schedule
• Rule-governed
• Language
• Generation of rules to govern behaviour, rather than just the reinforcement schedule
• Self- or externally-generated
• Young children more "animal-like"

Causes of FR Postreinforcement Pause

• Fatigue hypothesis
• Satiation hypothesis
• Remaining-responses hypothesis
• Reinforcer is a discriminative stimulus signaling absence of next reinforcer any time soon

Evidence

• Postreinforcement pause increases as FR size increases
• Does not support satiation
• Multiple FR schedules
• Long and short schedules
• PRP longer if next schedule long, shorter if next one short
• Does not support fatigue

Comparison of VR and VI Response Rates

• Response rate for VR faster than for VI
• Molecular theories
• Small-scale events
• Reinforcement on trial-by-trial basis
• Molar theories
• Large-scale events
• Reinforcement over whole session

IRT Reinforcement Theory

• Molecular theory
• IRT: Interresponse time
• Time between two consecutive responses
• VI schedule
• Long IRT reinforced
• VR schedule
• Time irrelevant
• Short IRT reinforced

Response-Reinforcer Correlation Theory

• Molar theory
• Response-reinforcer relationship across whole experimental session
• Long-range reinforcement outcome
• Trial-by-trial unimportant
• Criticism: too cognitive

(Figure 11)

Application: Teaching Language to Autistic Children

• Shaping
• Primary and conditioned reinforcers
• Prompts
• Any stimulus that makes a desired response more likely.
• Fading: gradual withdrawal of prompt
• Very intensive training program
• ~50% success

Application: Token Economies

• Conditioned reinforcers: tokens
• Earn tokens for appropriate behaviours
• Exchange tokens for primary reinforcer
• Fairly intensive to organize and maintain
• Fade out gradually, redirect from tokens to issues of self-satisfaction