Effects of reinforcement amount on attack induced under a fixed-interval schedule in pigeons.
Bigger reinforcers on fixed-interval schedules can triple adjunctive aggression in pigeons.
01Research in Context
What this study did
Duker et al. (1996) worked with pigeons on a fixed-interval food schedule. They doubled and tripled the grain portion per interval while filming pecks at a target bird.
Sessions lasted one hour. The team counted attacks after each payoff and tracked where in the hour the hits peaked.
What they found
More grain meant more attacks. Birds hit the target up to three times as often when the portion tripled.
The boost was strongest early in the session and faded as the hour passed. Procedural tweaks, like longer timeouts, softened but did not erase the jump.
How this fits with other research
Waite et al. (1972) first showed that the bare FI schedule itself sparks aggression. Duker et al. (1996) extends that work by proving bigger payoffs turn the same spark into a bigger flame.
Dardano (1970) saw attack rise with high fixed-ratio and extinction chunks. Duker et al. (1996) finds the same rule under fixed-interval: leaner or richer payoffs scale the side effect.
Rincover et al. (1975) looks like a contradiction — extra free food raised pigeons’ key peck rate, yet here extra food raised attacks. The key difference is contingency: the 1975 food was response-independent, while the 1996 food still required the interval to pass, keeping the aversive tension that triggers aggression.
Why it matters
When you thicken a reinforcement schedule — more tokens, longer play, extra screen time — watch for sudden spikes in problem behavior. Schedule out high-value reinforcers in smaller chunks or insert brief breaks to bleed off the tension that drives attack.
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02At a glance
03Original abstract
Key pecking by pigeons was maintained on a chained fixed-interval 4-min (12-min for 1 subject) fixed-ratio 1 schedule of food presentation. Attacks toward a restrained and protected conspecific were recorded. In the first experiment, the amount of food presented per interval was manipulated across phases by varying the number of fixed ratios required in the terminal link of the chain. Measures of attack for all pigeons during the fixed-interval component increased monotonically as a function of food amount. In the second experiment, two different food amounts alternated within each experimental session under a multiple schedule. For both pigeons in this experiment, measures of attack were higher during the component that delivered the larger food amount per interval. The differences in levels of attack induced by the two food amounts in Experiment 2, however, were not as great as in Experiment 1; apparently this was because attack during the first interval of each component was controlled in part (P-5626) or entirely (P-7848) by the reinforcement amount delivered at the end of the previous component. Attack was also a function of the location of the interfood interval within the session. For both pigeons, attack tended to decrease throughout the session. The results of both experiments suggest that attack is an increasing function of reinforcement amount under fixed-interval schedules, but that this function may be influenced by the manner in which reinforcement amount is manipulated, by the duration of the interfood interval, and by the location of the interfood interval within the experimental session. In general, these results are compatible with theories of induced attack and other schedule-induced behavior that emphasize aversive after-effects of reinforcement presentation.
Journal of the experimental analysis of behavior, 1996 · doi:10.1901/jeab.1996.65-93