Performances on ratio and interval schedules of reinforcement: Data and theory.
Post-reinforcement pauses, not weak operant strength, create the downturn on ratio schedules.
01Research in Context
What this study did
Pigeons worked on two schedules at once. One schedule was a variable ratio (VR). The other was a matched variable interval (VI). The two schedules gave the same number of reinforcers. The team watched every peck and every pause.
They then removed the short breaks that birds took after food. They wanted to see if the pause caused the drop in rate seen on ratio schedules.
What they found
Classic ratio strain showed up. Birds slowed or stopped when the VR requirement got large.
A surprise came in the VI part. Mid-range rates went up, not down.
When the team erased post-reinforcement pauses, the VR downturn vanished. The pause, not the running rate, drove the drop.
How this fits with other research
Halpern et al. (1966) first showed that pauses grow longer as fixed-ratio size grows. The new study keeps that story but adds a twist: pauses alone can hide real operant speed.
Guest et al. (2013) used the same yoked VR-VI setup twenty years later. They added tiny unsignaled delays. Delays boosted VI rates but left VR rates flat. This extends the target finding: pause-plus-delay effects differ by schedule type.
MIGLELong (1963) saw birds peck a change key when FR size got too big. That early sign of ratio strain matches the VR downturn here. The new data show the downturn is pause-driven, not a true drop in operant strength.
Garcia et al. (1973) ran concurrent FR-FI schedules. Birds matched response ratios to reinforcer ratios. The target paper agrees: pause time must be split out before you judge true response matching.
Why it matters
When a learner slows on a large ratio, do not assume the task is too hard. Clock the post-reinforcement pause first. If the pause shrinks and the rate looks fine, raise the ratio again. Treat pause and run as two separate behaviors in your data sheet.
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02At a glance
03Original abstract
TWO DIFFERENCES BETWEEN RATIO AND INTERVAL PERFORMANCE ARE WELL KNOWN: (a) Higher rates occur on ratio schedules, and (b) ratio schedules are unable to maintain responding at low rates of reinforcement (ratio "strain"). A third phenomenon, a downturn in response rate at the highest rates of reinforcement, is well documented for ratio schedules and is predicted for interval schedules. Pigeons were exposed to multiple variable-ratio variable-interval schedules in which the intervals generated in the variable-ratio component were programmed in the variable-interval component, thereby "yoking" or approximately matching reinforcement in the two components. The full range of ratio performances was studied, from strained to continuous reinforcement. In addition to the expected phenomena, a new phenomenon was observed: an upturn in variable-interval response rate in the midrange of rates of reinforcement that brought response rates on the two schedules to equality before the downturn at the highest rates of reinforcement. When the average response rate was corrected by eliminating pausing after reinforcement, the downturn in response rate vanished, leaving a strictly monotonic performance curve. This apparent functional independence of the postreinforcement pause and the qualitative shift in response implied by the upturn in variable-interval response rate suggest that theoretical accounts will require thinking of behavior as partitioned among at least three categories, and probably four: postreinforcement activity, other unprogrammed activity, ratio-typical operant behavior, and interval-typical operant behavior.
Journal of the experimental analysis of behavior, 1993 · doi:10.1901/jeab.1993.59-245