Response-independent events in the behavior stream.
Free food on a timer reshapes the moment-to-moment pattern of responding, not just the overall rate, and the shape depends on the NCR/VI ratio plus whether each schedule has its own signal.
01Research in Context
What this study did
The team gave pigeons food on a fixed-time schedule while the birds were already working for food on a variable-interval schedule. They watched how the extra, free food changed the birds' pecking pattern.
Sometimes the two schedules shared the same key color. Other times each schedule had its own color or its own key. The researchers varied how often the free food arrived compared with the birds' own earned food.
What they found
The free food did not just slow the birds down. It changed when they pecked. The size of the change hinged on two things: the ratio of free-food rate to earned-food rate, and whether each schedule looked different.
When the ratio was large and the schedules looked alike, pecks bunched up right after free food. When the ratio was small or the schedules looked different, the pattern flattened out.
How this fits with other research
Mann et al. (1971) saw that response-independent food could either suppress or boost responding, depending on the schedule context. The new study adds that the same food also sculpts the micro-timing of those responses.
Lattal (1974) showed that more free food means lower response rates. The 1997 data agree, but they reveal the drop is not smooth; it comes with rhythmic pauses and bursts tied to ratio and stimulus cues.
Heinicke et al. (2012) translated fixed-time food to preschool classrooms and cut problem behavior. The pigeon work warns that the reduction may look different if the NCR schedule ratio or classroom cues change.
Why it matters
If you run non-contingent reinforcement, do not just watch if behavior drops—watch when it drops. A high NCR/VI ratio with shared stimuli can create post-reinforcement pauses you might mistake for extinction bursts. Consider giving NCR its own distinct stimulus or toy so the learner can tell ‘free’ from ‘earned’ and the pattern stays flat.
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02At a glance
03Original abstract
The metaphor of the behavior stream provides a framework for studying the effects of response-independent food presentations intruded into an environment in which operant responding of pigeons was maintained by variable-interval schedules. In the first two experiments, response rates were reduced when response-independent food was intruded during the variable-interval schedule according to a concomitantly present fixed-time schedule. These reductions were not always an orderly function of the percentage of response-dependent food. Negatively accelerated patterns of key pecking across the fixed-time period occurred in Experiment 1 under the concomitant fixed-time variable-interval schedules. In Experiment 2, positively and negatively accelerated and linear response patterns occurred even though the schedules were similar to those used in Experiment 1. The variable findings in the first two experiments led to three subsequent experiments that were designed to further illuminate the controlling variables of the effects of intruded response-independent events. When the fixed and variable schedules were correlated with distinct operanda by employing a concurrent fixed-interval variable-interval schedule (Experiment 3) or with distinct discriminative stimuli (Experiments 4 and 5), negatively accelerated response patterns were obtained. Even in these latter cases, however, the response patterns were a joint function of the physical separation of the two schedules and the ratio of fixed-time or fixed-interval to variable-interval schedule food presentations. The results of the five experiments are discussed in terms of the contributions of both reinforcement variables and discriminative stimuli in determining the effects of intruding response-independent food into a stream of operant behavior.
Journal of the experimental analysis of behavior, 1997 · doi:10.1901/jeab.1997.68-375