Effects Of Histories Of Differential Reinforcement Of Response Rate On Variable-interval Responding

Three pigeons were exposed first to multiple differential-reinforcement-of-high-rate and differential-reinforcement-of-low-rate schedules that were correlated with green and red keys, respectively, and then were shifted to a variable-interval schedule arranged on a white key. In subsequent test sessions, the variable-interval schedule continued to operate, but green and red keys replaced the white key in alternate sessions. In Part 1 of the experiment, the variable-interval schedule correlated with the white key was introduced immediately after the multiple-schedule condition, and the test condition began 15 days later. This sequence was repeated twice, with a reversal of the correlation of the key colors with the components of the multiple schedule at the start of each new cycle. Part 2 added a 6-month break between the multiple-schedule history and the white-key variable-interval schedule followed by test sessions. The procedure was then repeated with a reversal of the correlation between key colors and multiple-schedule components. In the test sessions of Part 1, all pigeons consistently responded faster in the presence of the key color most recently correlated with the differential-reinforcement-of-high-rate contingency than during the color most recently correlated with the differential-reinforcement-of-low-rate contingency. Similar but smaller effects were observed in Part 2. The effects of the reversals in these two parts of the experiment showed that only the most recent contingency exerted an influence on subsequent responding. The data suggest that this effect of the most recent history continues to operate on behavior under current contingencies even after a long lapse of time.     

Stimulus properties of conspecific behavior

Two experiments identified the conditions in which the behavior of one bird acquired discriminative control of the behavior of a second bird. The schedule-controlled behaviors of the “stimulus” bird were differentially correlated with the components of a multiple schedule according to which the pecking of an “experimental” bird produced food. In Experiment 1, three pairs of pigeons acquired a successive discrimination and two reversals with the conspecific stimuli. Experiment 2 included a control condition in which no systematic relationship existed between the conspecific stimuli and the component schedules. While differential responding during the components of the multiple schedule was again found when the conspecific stimuli were available, differential responding did not occur in the control condition. Test conditions included in the experiments indicated that (a) the differential responding was not dependent on the discriminative properties of reinforcement, (b) the pecking of the stimulus and experimental birds was temporally interrelated, (c) the visual conspecific stimuli were critical to the maintenance of the discrimination, and (d) the observed stimulus control immediately generalized to an unfamiliar conspecific.