Reinforcement schedules: Retroactive and proactive effects of reinforcers inserted into fixed-interval performances.
Inserted reinforcers block earlier responses from future payoff, and any carry-over comes from the cues paired with them, not the extra reward.
01Research in Context
What this study did
The team used fixed-interval (FI) schedules with pigeons.
They slipped extra short-FI reinforcers into the middle of longer FI periods.
Then they watched how these inserted rewards changed later response patterns.
What they found
Short-FI reinforcers blocked the backward pull of later long-FI reinforcers.
Forward effects came from stimulus cues, not the extra food itself.
Each reinforcer acts like a wall, sealing off earlier responses from future payoff.
How this fits with other research
Schwartz (1969) saw the same FI scallop stay intact after local tweaks.
That supports the new finding: long-term history, not single reinforcers, shapes the curve.
Adkins et al. (1997) later showed DRH vs DRL history still skewed VI rates months later.
Their long-lasting bias looks like a proactive effect, but C et al. say such carry-over is cue-driven, not food-driven.
Together the papers agree: past schedules echo forward, yet the echo’s source is discriminative stimuli, not leftover reinforcer power.
Why it matters
When you design thinning schedules, remember each reinforcer wipes the slate for earlier responses.
If you insert extra praise or tokens, expect them to shield prior behavior from later payoff.
Check what cues come with the bonus, because the cue—not the bonus itself—will guide next responding.
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02At a glance
03Original abstract
The responding maintained by a reinforcer depends on the relation of the reinforcer not merely to the response that produces it but also to other preceding responses. Early responses in a sequence that ends in a reinforcing consequence make smaller contributions to later response rates than more recent ones, by virtue of the longer delays that separate them from the reinforcer. This study shows that the relation between a response and a later reinforcer contributes to responding only if no other reinforcers intervene; in other words, each reinforcer blocks responses that precede it from the effects of later reinforcers. Pigeons' pecks were maintained by fixed-interval (FI) schedules of food reinforcement. When FI 60-s (short) and FI 75-s (long) schedules began simultaneously within constant 150-s cycles, long FIs did not affect short-FI performances, but short FIs eliminated the first 60 s of long-FI performances. Removing either short-FI reinforcers or short-FI stimuli showed that short-FI reinforcers and not short-FI stimuli blocked the first 60 s of the long-FI performance from the retroactive effects of the long-FI reinforcer. With FI 15-s and FI 75-s schedules, the short-FI reinforcer was followed by reduced long-FI responding, but a schedule that prevented discrimination based on time since a reinforcer eliminated this proactive effect of the short-FI reinforcer. In other words, the retroactive effects were reinforcer effects whereas the proactive effects were discriminative effects. Quantitative descriptions of variable-interval performances, in which reinforcer effects may operate in the absence of temporal discriminative effects, can be derived from these relations.
Journal of the experimental analysis of behavior, 1988 · doi:10.1901/jeab.1988.49-49