Schedule-induced biting under fixed-interval schedules of food or electric-shock presentation.
Schedule-induced biting peaks at middle FI lengths and can be toned down with timeout or drugs.
01Research in Context
What this study did
Carroll (1977) tested monkeys on fixed-interval food or shock delivery. The team watched for biting after each reward.
They changed the interval length and added brief timeouts or a dose of amphetamine. Biting rose, then fell, as the interval grew.
What they found
Biting followed an upside-down U. It peaked at middle-length intervals and dropped at very short or very long ones.
A short timeout or the drug shifted the peak, showing the biting was truly schedule-induced, not random aggression.
How this fits with other research
Anger et al. (1976) saw the same curve with drinking instead of biting. Same monkeys, same schedule—only the behavior changed. This backs the idea that the schedule, not the topography, drives the curve.
Waite et al. (1972) first spotted post-food attack in pigeons under FI schedules. Carroll (1977) widened the lens to monkeys and added drug tests, extending the finding across species and controls.
Brown et al. (1972) recorded escape that also peaked at mid-length FI values. Together these papers show that many adjunctive responses—escape, attack, biting—share the same inverted-U footprint.
Why it matters
If you run FI schedules in the lab or teach with them, watch for collateral behavior. Post-reinforcement biting, drinking, or escape all surge most at moderate intervals. Build in brief timeouts or stretch the interval if these behaviors appear—they reliably knock the peak down.
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02At a glance
03Original abstract
Squirrel monkeys pressed a lever under fixed-interval schedules of food or of electric-shock presentation. Both schedules induced repeated biting on a latex hose. Whether lever pressing was controlled by food or by electric shock, a pattern of decreasing hose biting and increasing lever pressing occurred within fixed-interval cycles. As the fixed-interval duration was increased from 6 to 600 sec, average rates of lever pressing decreased under both schedules. Average rates of hose biting first increased with increasing parameter value, reaching a maximum at values that varied from 60 to 337 sec in different monkeys, and then declined at higher values. d-Amphetamine at appropriate doses increased overall rates of lever pressing maintained by food or by shock, but either did not affect or decreased overall rates of hose biting. When no timeout period occurred between fixed-interval cycles, the monkeys bit most frequently immediately after food or electric shock was presented. When there was a timeout period, hose biting began shortly after the start of the fixed-interval cycles, with little or no hose biting immediately after food or electric shock was presented. Most hose biting appeared to be schedule-induced rather than food- or shock-induced.
Journal of the experimental analysis of behavior, 1977 · doi:10.1901/jeab.1977.27-419