ABA glossary
Fixed ratio
Also called FR
Definition
A schedule in which reinforcement follows a set number of responses, such as every fifth response on FR 5. FR 1 is the same as continuous reinforcement.
In plain words
On a fixed ratio, the learner always does the same amount of work to earn reinforcement. Only the count matters, not the time, so a faster responder earns reinforcement sooner. FR schedules typically produce a high rate of responding with a pause right after each reinforcer (the post-reinforcement pause), and the pause tends to grow as the ratio gets larger. Piecework pay is the familiar everyday example.
Example from a session
Sam earns 3 minutes of tablet time after every 5 completed matching tasks (FR 5). The RBT counts completed tasks on the data sheet and delivers the tablet as soon as the fifth one is done. She notices that Sam pauses briefly after each tablet break before starting the next task, a typical fixed-ratio pattern, and keeps following the schedule exactly as the plan states.
For BCBA candidates and supervisors
Large ratios, or ratios raised too quickly, can produce ratio strain: long pauses, escape behavior, or responding that stops. When thinning, analysts raise the ratio in small steps and go back to the last requirement that worked if strain appears. A predictable work requirement can help some learners, but variable ratios usually produce steadier responding with less pausing, so FR is often a starting point rather than the end point of a thinning plan.
Often confused with variable ratio, fixed interval
On a fixed ratio the number of responses never changes; on a variable ratio it changes from one reinforcer to the next around an average. On a fixed interval, the count does not matter at all: only time, then one response. "Every 10th response" is FR 10, "on average every 10th response" is VR 10, and "the first response after 10 minutes" is FI 10 min.
Exam tip
Fixed ratio means the same count every time. If a stem says "every" plus a number of responses, it is FR, and the expected pattern is a high rate with a pause after each reinforcer.
Can you spot fixed ratio in a scenario?
Practice BCBA B.9 with exam-style questions and instant feedback.