In operant conditioning, a simple reinforcement schedule in which reward is delivered after the organism has made a fixed number of responses, and is delivered again after the same number of responses, and so on, the number of responses required before each reinforcement being specified as an affix to the abbreviation, hence FR10 indicates a fixed-ratio schedule with reinforcement after every 10 responses. Also called a fixed-ratio reinforcement schedule. See also simple reinforcement schedule. Compare fixed-interval schedule, variable-interval schedule, variable-ratio schedule. FR abbrev.