Behaviour of Rats During Selfinitiated Pauses in Feeding and Drinking, and during Periodic Response-Independent Delivery of Food and Water

In Experiment I rats deprived of either food or water were given free access to food or water respectively, and their behaviour was observed during self-imposed pauses in feeding or drinking. In Experiment II food or water were delivered according to fixed-time 30-s and fixed-time 60-s schedules, and the behaviour of the rats was observed during the interreinforcement intervals imposed by these schedules. In both experiments the temporal pattern of those activities that occurred during pauses in eating differed from the pattern of activities occurring during pauses in drinking; and with both food and water the temporal pattern of activities during self-imposed pauses in consummatory behaviour in Experiment I proved a good predictor of the pattern of activities during schedule-imposed interreinforcement intervals in Experiment II. This suggests that intermittent schedules permit the occurrence of those activities that are normally closely associated with the consummatory behaviour in question. In Experiment II certain activities that occurred towards the end of the interreinforcement interval were found to be enhanced relative to baseline level, but there was no enhancement of activities occurring near the beginning of the interval. This is contrary to Staddon's (1977) account of schedule-induced behaviour, and suggests that schedule-induction is not as common as has sometimes been supposed.

Changes in Rate of Schedule-Induced Behaviour in Rats as a Function of Fixed-Interval Schedule

Two experiments were conducted to determine the way in which rate of adjunctive drinking and food-tray responding vary as a function of interreinforcement interval duration. In Experiment I rats were tested under fixed-interval schedules ranging from 1–60 s in duration, and in Experiment II under fixed-interval schedules ranging from 1–180 s in duration, with food as the reinforcer. The rate of drinking increased and then declined as interreinforcement interval increased, reaching a maximum under intervals of about 45 s. The rate of food-tray responding declined over the whole range of schedules. It is concluded that drinking can meaningfully be described as “schedule-induced”, in the sense of being directly facilitated by intermittent schedules of reinforcement; but this is less certain in the case of food-tray responding.

The “Gambler Effect”: Choice and the Probability of Reinforcement of Small Response Outputs

Several types of concurrent-chains studies in which preference was found disproportionate to the rate of primary reinforcement were discussed. The disproportionality was attributed to the unusual effect on preference of the smallest interreinforcement interval components of schedules of reinforcement. The present study investigated an aspect of this factor in the control of preference. Concurrently available fixed-ratio 10 schedules were chained to a fixed-ratio 30 schedule on one key and a multiple fixed-ratio 5 fixed-ratio 80 on the alternative key. In the course of the study the relative frequency of the smallest interreinforcement interval (FR 5) in the multiple schedule option was reduced from 0.50 to 0. Pigeons could maximize reinforcement by always choosing the FR 30 schedule or choosing the multiple schedule and “gambling” that the FR 5 would be produced. Three pigeons chose the multiple schedule exclusively with one exception until the FR 5 was removed entirely from the multiple schedule. At this point, all birds chose the fixed schedule exclusively. Preference defined as rate of initial links responding was, in most instances, inversely related to rate of primary reinforcement.