Changes in functional response units with briefly delayed reinforcement.
A silent half-second delay can turn single responses into bursts and change how behavior is grouped.
01Research in Context
What this study did
Sievert et al. (1988) worked with pigeons on a variable-interval food schedule.
They added tiny, silent delays of 0.5 s or 5 s between each peck and the grain hopper.
The team then counted how long the birds waited between pecks.
What they found
The 0.5-s silent delay made the birds peck faster and in tight bursts.
The 5-s silent delay did the opposite; birds slowed down and spread out their pecks.
The authors said the short delay turned one peck into a functional unit of several pecks.
How this fits with other research
Wolchik et al. (1982) saw the same speed-up with 0.5-s delays six years earlier, so the burst pattern is reliable.
Guest et al. (2013) later showed the speed-up only happens on interval schedules, not on ratio schedules, setting a clear boundary.
Muething et al. (2018) moved the idea into a classroom: adding a short wait before giving a toy helped children with autism ask for new things instead of repeating the same word.
Together, the four studies show that a brief, unsignaled pause can reshape response units in both birds and humans.
Why it matters
If you deliver reinforcement too soon, you may accidentally strengthen rapid, repetitive responses.
Try inserting a tiny, silent half-second pause before giving the edible or toy.
Watch whether the learner slows down, varies words, or tries new mands.
This simple timing tweak can expand functional communication without extra teaching steps.
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02At a glance
03Original abstract
In two experiments, key-peck responding of pigeons was compared under variable-interval schedules that arranged immediate reinforcement and ones that arranged unsignaled delays of reinforcement. Responses during the nominal unsignaled delay periods had no effect on the reinforcer presentations. In Experiment 1, the unsignaled delays were studied using variable-interval schedules as baselines. Relative to the immediate reinforcement condition, 0.5-s unsignaled delays decreased the duration of the reinforced interresponse times and increased the overall frequency of short (<0.5-s) interresponse times. Longer, 5.0-s unsignaled delays increased the duration of the reinforced interresponse times and decreased the overall frequency of the short interresponse times. In Experiment 2, similar effects to those of Experiment 1 were obtained when the 0.5-s unsignaled delays were imposed upon a baseline schedule that explicitly arranged reinforcement of short interresponse times and therefore already generated a large number of short interresponse times. The results support earlier suggestions that the unsignaled 0.5-s delays change the functional response unit from a single key peck to a multiple key-peck unit. These findings are discussed in terms of the mechanisms by which contingencies control response structure in the absence of specific structural requirements.
Journal of the experimental analysis of behavior, 1988 · doi:10.1901/jeab.1988.49-249