AP Syllabus focus:
‘Different reinforcement schedules, including continuous and partial, affect the strength and pattern of behavior.’
Reinforcement schedules describe when consequences follow behavior. They are used to predict how quickly a response is learned, how persistent it becomes, and the characteristic pattern of responding that emerges over time.
Core idea: “When is reinforcement delivered?”
Reinforcement schedules
Reinforcement schedule: a rule that specifies the pattern and timing with which a reinforcer is delivered following a behavior.
Schedules shape two key outcomes:
Response acquisition: how rapidly a behavior increases.
Resistance to extinction: how long the behavior persists when reinforcement stops.
Continuous vs partial (intermittent) reinforcement
Continuous reinforcement (CRF)
Continuous reinforcement means reinforcing every correct response.
Typically produces fast learning.
Often produces low resistance to extinction (behavior drops quickly once reinforcement ends).
Useful early in training when the goal is clear acquisition.
Partial (intermittent) reinforcement
Partial (intermittent) reinforcement: reinforcing a response only some of the time, according to a specific schedule.
Partial reinforcement often produces slower acquisition but greater persistence.
A major implication is the partial reinforcement effect: behaviors learned under partial reinforcement tend to be more resistant to extinction than behaviors learned under continuous reinforcement.
The four classic partial reinforcement schedules
Cumulative-record graph comparing fixed ratio (FR), variable ratio (VR), fixed interval (FI), and variable interval (VI) schedules. The slope reflects response rate, while the distinct shapes illustrate hallmark patterns such as the FR post-reinforcement pause and FI scalloping. This visual makes it easy to connect schedule type to both the rate and the pattern of responding. Source
Ratio vs interval, fixed vs variable
Two dimensions determine the schedule:
Ratio schedules: reinforcement depends on the number of responses.
Interval schedules: reinforcement depends on time passing. And:
Fixed: predictable, consistent requirement.
Variable: requirement changes unpredictably around an average.
Ratio schedules (response-based)
Fixed ratio (FR)
In a fixed ratio schedule, reinforcement occurs after a set number of responses.
Common response pattern: high rate with a post-reinforcement pause (a brief drop right after reinforcement).
Tends to build strong responding because “more responding = more reinforcement.”
Variable ratio (VR)
In a variable ratio schedule, reinforcement occurs after an unpredictable number of responses (around an average).
Common response pattern: very high, steady responding with minimal pausing.
Typically produces very strong resistance to extinction, because reinforcement is never “due” at a known moment.
Interval schedules (time-based)
Fixed interval (FI)
In a fixed interval schedule, the first response after a fixed amount of time is reinforced.
Common response pattern: scalloping—responding increases as the expected time of reinforcement approaches, then drops after reinforcement.
Diagram illustrating the fixed-interval “scallop” pattern of responding. After each reinforcement, responding pauses and then accelerates as the next reinforcement opportunity approaches, producing a repeating, curved rise in cumulative responses over time. This is the classic visual signature used to identify FI schedules on cumulative records. Source
Can produce uneven performance because early responses in the interval are unlikely to be reinforced.
Variable interval (VI)
In a variable interval schedule, the first response after a varying amount of time is reinforced.
Common response pattern: steady, moderate responding.
Encourages consistent checking/responding since reinforcement timing is uncertain.
How schedules affect “strength” and “pattern” of behavior
Strength (persistence)
Continuous: weaker persistence when reinforcement stops.
Partial: stronger persistence, especially variable schedules (uncertainty promotes continued responding).
Pattern (response rate and shape)
Ratio schedules generally yield higher response rates than interval schedules.
Fixed schedules create predictable pauses or bursts (e.g., post-reinforcement pause; scalloping).
Variable schedules create steady responding because the next reinforcer cannot be precisely anticipated.
FAQ
With variable schedules, reinforcement is not “due” at a predictable moment.
This reduces pausing and promotes consistent responding because any response could be the one that is reinforced.
Schedule thinning is gradually shifting from frequent reinforcement to less frequent reinforcement while maintaining behaviour.
It is used to make behaviour more durable in real-world settings where reinforcement cannot occur every time.
Schedules determine when reinforcement happens, while magnitude determines how valuable it is.
Larger or more preferred reinforcers can maintain responding even on leaner schedules, but may also produce satiation more quickly.
Yes, in concurrent or compound arrangements, more than one contingency can influence responding.
This can shift behaviour allocation toward the option with higher reinforcement rate, lower effort, or more immediate reinforcement.
Very demanding ratio schedules can lead to:
“Ratio strain” (breakdown of responding)
Frustration or avoidance of the task
Balancing response effort and reinforcement rate helps maintain stable behaviour.
Practice Questions
Outline one difference between a fixed interval schedule and a variable interval schedule. (2 marks)
1 mark: FI delivers reinforcement for the first response after a set period of time / predictable timing.
1 mark: VI delivers reinforcement for the first response after varying periods of time / unpredictable timing around an average.
Explain how reinforcement schedules can affect both the pattern of responding and resistance to extinction, referring to continuous reinforcement and one partial schedule. (6 marks)
1 mark: Continuous reinforcement strengthens behaviour quickly because every response is reinforced.
1 mark: Continuous reinforcement tends to produce low resistance to extinction (behaviour drops rapidly when reinforcement stops).
1 mark: Correctly identifies one partial schedule (FR/VR/FI/VI).
1 mark: Describes the typical response pattern for the chosen schedule (e.g., VR = high steady responding; FI = scalloping; FR = post-reinforcement pause; VI = steady moderate responding).
1 mark: Explains why partial reinforcement increases resistance to extinction (uncertainty/learning that reinforcement is not guaranteed each time).
1 mark: Links schedule properties (ratio vs interval; fixed vs variable) to either response rate or predictability of responding.
