PS261 Chapter Notes - Chapter 6: Matching Law, Human Behaviour, Impulsivity
Chapter 6 − Schedules of Reinforcement & Choice Behaviour
6.1: Introduction
Intro to Schedules of Reinforcement
- Schedule of Reinforcement: program/rule that determines which occurrence of a
response is followed by the reinforcer
o Delivery of the reinforcer could depend on many factors, including:
▪ Certain number of responses
▪ Passage of time
▪ Presence of certain stimuli
▪ Occurrence of other responses
- Applications of reinforcement principles typically have a behaviour goal
o Achieving the goal often requires adjusting the schedule of reinforcement to
produce the desired outcome
- Schedules of reinforcement influence both how an instrumental response is learned, and
how it is then maintained by reinforcement
o Concerned with the maintenance of behaviour
▪ Highly relevant to the motivation of behaviour
o Provide useful baselines for the study of other behavioural processes
- Conducted using a Skinner Box − has a clearly-defined response that can occur repeatedly
o Changes in rate of responding can be readily observed and analyzed
- Focus is on:
o Scheduled factors that control the timing and respective performance of behaviour
6.2 − Simple Schedules of Intermittent Reinforcement
6.2.a
−
Introduction to Schedules of Reinforcement
- In simple schedules, a single factor determines which occurrence of the instrumental
response is reinforced
o Partial/Intermittent Reinforcement: delivers reinforcement for some responses
- Four simple schedules of intermittent reinforcement:
o
6.2.b
−
Ratio Schedules
- Ratio Schedule: reinforcement depends on number of responses the organism has performed
o Can be delivered after a fixed or variable (average) number of responses
- Fixed Ratio Schedule: delivers reinforcement after every nth response
o A continuous reinforcement schedule is also a fixed ratio schedule
▪ Delivers reinforcement for every occurrence of the response
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- Cumulative Record: special way of representing how a response is repeated over time
o The slope of the line made by this is a visual representation of when and how
frequently the subject responds during a session
o Post-Reinforcement Pause: the rate of responding that occurs just after
reinforcement
▪ Pattern of Responding
▪ The length of the pause is controlled by the upcoming ratio requirement
o Ratio Run: the high and steady rate of responding that completes each ratio
requirement
▪ Pattern of Responding
- Variable Ratio Schedule: average number of responses required per reinforcer
o Delivers reinforcement after a variable number of responses
o Steady rate of responding
▪ No predictable pauses
6.2.c
−
Interval Schedules
- Interval Schedule: responses are reinforced only if they occur after a certain amount of
time has passed
o Can be delivered after a fixed or variable (average) amount of time
- Fixed Interval Schedule: the amount of time that has to pass before a reinforcement is
constant from one trial to the next
o Reinforcement is delivered for the first response that occurs after a fixed period of
time has elapsed
o Found in situations where a fixed amount of time is required to prepare/set up the
reinforcer
o FI Scallops: the subject learns to withhold responding until the end of the interval,
and then suddenly increases their response rate
▪ Pattern of Responding
- Variable Interval Schedule: responses are reinforced only if they occur after a variable
interval after the start of the trial or schedule cycle
o Reinforcement is delivered for the first response that occurs after a variable period
of time has elapsed
o Steady rate of responding with no pauses
▪ Pattern of Responding
- Limited Hold: restriction on how long a reinforcer remains available
o Can be added to both fixed interval and variable interval schedules
6.2.d
−
Comparison of Schedules
- With both fixed ratio (FR) and fixed interval (FI) schedules, there is a post-reinforcement
pause after each delivery of the reinforcer
o Both produce high rates of responding just before the delivery of the next reinforcer
- Variable ratio (VR) and Variable Interval (VI) schedules both maintain steady rates of
responding, with no predictable pauses
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- Both FR and VR produce higher rates of responding than FI and VI
- Research:
o Reynolds − compared rate of key pecking on VR and VI
▪ Found higher response rate for VR than VI
- Reinforcement of IRTS
o Inter-Response Time (IRT) − focuses on the spacing/interval between one
response and the next
▪ Rate of responding for ratio schedules is higher than interval, due to IRT
• If the subject is reinforced for a response that occurs shortly after
the preceding one − a short IRT is reinforced, and short IRTs
become more likely in the future
o Ratio schedule favors not waiting long between responses
▪ Differentially reinforces short IRTs − favors short IRTs
▪ Results in higher rates of responding
o Interval schedule favors waiting longer between responses
▪ Differentially reinforces long IRTs − favors long IRTs
▪ Results in lower rates of responding
- Feedback Functions: relationship between response rates and reinforcement rates
calculated over an entire experimental session or an extended period of time
o Reinforcement is considered to be the feedback or consequence of responding
o With ratio schedules, response rate is directly related to reinforcement rate
▪ No upper limit on amount of reinforcement that can be earned
o Interval schedules place an upper limit on the number of reinforcers a subject can earn
▪ Each trial begins with a period during which reinforcer is not available −
there is an upper limit to the number of reinforcers a subject can earn
▪ Response rate is not directly related to reinforcement rate
6.3 − Choice Behaviour: Concurrent Schedules
- The simplest choice situation is one which has two response alternatives, and each
response is followed by a reinforcer according to its own schedule of reinforcement
o The two schedules are in effect at the same time (concurrently), and the subject is
free to switch from one response key to the other
- Concurrent Schedule: subject is given a choice between two responses
o Each choice corresponds to a specific schedule of reinforcement
o Interested in how the subject distributes their responses between the two choices
6.3.a
−
Measures of Choice Behaviour
- Relative Rate of Responding = BL/(BL+BR)
o BL: rate of responding on left key; BR: rate of responding on right key
▪ L − left; B − behaviour; R − right
o Where the animal spends most of their time responding is where they are getting
the most reinforcement
o If the response rate is equal, the ratio will be 0.5
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Document Summary
Chapter 6 schedules of reinforcement & choice behaviour. Applications of reinforcement principles typically have a behaviour goal: achieving the goal often requires adjusting the schedule of reinforcement to produce the desired outcome. Conducted using a skinner box has a clearly-defined response that can occur repeatedly: changes in rate of responding can be readily observed and analyzed. Focus is on: scheduled factors that control the timing and respective performance of behaviour. In simple schedules, a single factor determines which occurrence of the instrumental response is reinforced: partial/intermittent reinforcement: delivers reinforcement for some responses. Ratio schedule: reinforcement depends on number of responses the organism has performed: can be delivered after a fixed or variable (average) number of responses. Fixed ratio schedule: delivers reinforcement after every nth response: a continuous reinforcement schedule is also a fixed ratio schedule, delivers reinforcement for every occurrence of the response.
