Conjunctive schedules of reinforcement: III. A fixed-interval adjusting fixed-ratio schedule.
Tacking a small adjustable ratio onto a fixed-interval schedule sharpens performance, but push the ratio too high and the whole pattern falls apart.
01Research in Context
What this study did
Pigeons pecked a key for food on a fixed-interval schedule.
The birds also had to finish a small, changing number of extra pecks.
The extra ratio started low and went up or down based on the last bird’s speed.
What they found
Small-to-medium extra ratios made the post-food pause longer and the run faster.
Big extra ratios flipped the pattern: pauses shrank, runs slowed, and some birds quit.
Too much work on top of the timer wrecked the smooth scallop shape.
How this fits with other research
Halpern et al. (1966) first showed bigger pure FR schedules make pauses longer. Lea (1976) proves the same rule holds when the ratio rides on top of an FI.
Rogers-Warren et al. (1976) layered free food on an FI and saw the scallop flatten. Lea (1976) layers required work instead and finds the scallop can sharpen or break, not just flatten.
Hart et al. (1980) added only a counter to an FR and still got longer pauses. Lea (1976) shows the pause grows only when the added work is modest; push it too high and the bird gives up—an apparent contradiction explained by workload size.
Why it matters
When you stack extra tasks on a timed reinforcement plan, keep the add-on small. A little extra work tightens the learner’s timing; too much crashes motivation and fluency. Test the ratio in tiny steps and watch for pause or rate collapse.
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02At a glance
03Original abstract
Key pecking of three pigeons was studied under a conjunctive schedule that specified both a fixed-interval and an adjusting fixed-ratio requirement. The fixed-interval schedule was 6 min for one pigeon and 3 min for the other two. The size of the ratio requirement was determined within each cycle of the fixed interval by the duration of the pause before responding began. The fixed-ratio value was at maximum at the start of each fixed interval and decreased linearly until the first response occurred (adjusting fixed-ratio schedule). A peck produced food when the number of responses remaining on the fixed-ratio schedule was completed and when the fixed interval had elapsed. If no response occurred during the interval, the fixed-ratio requirement decreased to one and a single response after the interval elapsed produced food. The initial value of the adjusting fixed-ratio schedule was studied over a range of 0 to 900. Increases in the adjusting fixed-ratio schedule to about 300 responses increased both pause duration and running response rate and also modified the pattern of responding from that obtained under the fixed-interval schedule. Higher values of the adjusting fixed ratio generally decreased pause duration and running response rate and also disrupted responding. Interreinforcement time under the conjunctive schedule was increased substantially when the adjusting fixed-ratio size exceeded 300 responses.
Journal of the experimental analysis of behavior, 1976 · doi:10.1901/jeab.1976.25-157