Schedule-induced mirror responding in the pigeon.
Mirror pecks in pigeons follow the same inverted-U function with FR size that schedule-induced aggression and drinking follow, pointing to a general law of adjunctive behavior.
01Research in Context
What this study did
Researchers placed pigeons on a multiple fixed-ratio schedule. Birds earned food every 30, 60, or 120 responses.
A small mirror sat next to the food hopper. The team filmed how often each bird pecked its reflection before and after food arrived.
What they found
Mirror pecks rose and fell like an upside-down U. Few pecks at FR 30, most at FR 60, fewer again at FR 120.
The pattern matched the birds’ schedule-induced attack seen in earlier work. Longer waits for food meant more mirror contact right after the grain was eaten.
How this fits with other research
Dardano (1970) saw the same curve with aggression three years earlier. S et al. simply swapped the target: mirror instead of another bird.
Anger et al. (1976) later repeated the upside-down U in monkeys that drank too much water between pellets. Same rule, new species and behavior.
Duker et al. (1996) bumped up food portion per FI cycle and got more attack. Together the papers show adjunctive behavior grows when food is regular but not too easy or too scarce.
Why it matters
If you run dense fixed-ratio or fixed-interval programs, watch for extra behaviors that tag along. A child might tap the desk, bite nails, or stare at mirrors exactly like these pigeons. Track the timing: the peak usually sits in the middle effort range. Thin or thicken the schedule, or give a quick incompatible task right after reinforcement, to keep these adjuncts low.
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Join Free →Graph any unusual post-reinforcement behavior across your current FR sizes; if you see a mid-range spike, try shortening the ratio or inserting a brief toy play to disrupt the adjunctive burst.
02At a glance
03Original abstract
Two pigeons that were previously exposed to a multiple schedule of reinforcement in the presence of a stuffed and a live pigeon, and two of three naive pigeons, responded on a mirror during exposure to multiple fixed-ratio, fixed-ratio schedules of reinforcement for key pecking. Both the topography and temporal pattern of mirror responding were comparable to schedule-induced "attack" on live and stuffed targets. Rate of target responding was reduced when either the mirror was covered with paper or when the multiple schedule was removed. A reversal in the relationship between reinforcement schedules and discriminative stimuli demonstrated that mirror responding was controlled by the stimulus correlated with the higher fixed-ratio schedule. With one component of the multiple schedule held constant at fixed ratio 25 and the ratio requirement of the other component varying from 25 to 150, there was an inverted U-shaped relationship between rate of mirror responding and fixed-ratio schedule in the varied component. As in Flory's study (1969b) there was an inverted U-shaped relationship between target responding and inter-food intervals. The combined results of these studies suggest that the relationship between rate of target responding and reinforcement schedules is controlled primarily by the inter-food intervals resulting from the schedules.
Journal of the experimental analysis of behavior, 1973 · doi:10.1901/jeab.1973.19-395