EFFECTS OF REINFORCEMENT AMOUNT ON ATTACK INDUCED UNDER A FIXED-INTERVAL SCHEDULE IN PIGEONS

Key pecking by pigeons was maintained on a chained fixed-interval 4-mi n (12-min for 1 subject) fixed-ratio 1 schedule of food presentation. Attacks toward a restrained and protected conspecific were recorded. I n the first experiment, the amount of food presented per interval was manipulated across phases by varying the number of fixed ratios requir ed in the terminal link of the chain. Measures of attack for all pigeo ns during the fixed-interval component increased monotonically as a fu nction of food amount. In the second experiment, two different food am ounts alternated within each experimental session under a multiple sch edule. For both pigeons in this experiment, measures of attack were hi gher during the component that delivered the larger food amount per in terval. The differences in levels of attack induced by the two food am ounts in Experiment 2, however, were not as great as in Experiment 1; apparently this was because attack during the first interval of each c omponent was controlled in part (P-5626) or entirely (P-7848) by the r einforcement amount delivered at the end of the previous component. At tack was also a function of the location of the interfood interval wit hin the session. For both pigeons, attack tended to decrease throughou t the session. The results of both experiments suggest that attack is an increasing function of reinforcement amount under fixed-interval sc hedules, but that this function may be influenced by the manner in whi ch reinforcement amount is manipulated, by the duration of the interfo od interval, and by the location of the interfood interval within the experimental session. In general, these results are compatible with th eories of induced attack and other schedule-induced behavior that emph asize aversive aftereffects of reinforcement presentation.