Temporal Averaging Across Stimuli Signaling the Same or Different Reinforcing Outcomes in the Peak Procedure

The present study examined factors that affect temporal averaging in rats when discriminative stimuli are compounded following separate training indicating the availability of reward after different fixed intervals (FI) on a peak procedure. One group of rats, Group Differential, learned that a flashing light stimulus signaled that one type of food pellet reward could be earned for lever pressing after an FI 5 s interval and that a second type of food pellet reward could be earned after an FI 20 s interval in the presence of a tone stimulus. A second group of rats, Group Non-Differential, was similarly trained except that both types of rewards were scheduled across flash and tone trials. When given non-reinforced flash + tone compound test trials the interval containing the maximal response rate was no different than on flash alone test trials, although some responding also appeared near the long FI time. After these FI contingencies were reversed (flash signaled FI 20 s and tone signaled FI 5 s), however, further compound test trials more clearly revealed a temporal averaging pattern in both groups. The peak interval was shifted to the right of the FI 5 stimulus. Moreover, Group Differential rats acquired the reversed discrimination somewhat more rapidly than Group Non-Differential rats, and in a final selective satiation test Group Differential rats responded less in later intervals after they had been sated on the FI 20 s reward. These data suggest that temporal averaging in stimulus compound tests occurs even when the stimuli being combined signal qualitatively different rewards, but that decreasing the value of one of those rewards can shift responding away from the relevant time interval in a selective satiation test. However, when an especially salient stimulus (e.g., flashing light) signals a short FI, rats tend to process the compound stimulus more in terms of its individual elements.

Relative Efficacy of Video versus Food-Pellet Reward of Joystick Tasks

We suggest that the data reported by Washburn and Hopkins in their comment on our demonstration of the efficacy of live-video reward of joystick tasks supports, rather than impeaches, our earlier findings.

Videotape- versus Pellet-Reward Preferences in Joystick Tasks by Macaques

Andrews and Rosenblum (1993) convincingly demonstrated the effectiveness of live-social-video reward for joystick-task performance by bonnet macaques. We performed a similar series of experiments with quite different results. Taken together, these experiments emphasize the importance of the variability in individual preferences for reward effectiveness.

Live-Social-Video Reward Maintains Joystick Task Performance in Bonnet Macaques

A number of studies have now indicated that monkeys of several species will perform hundreds of food-rewarded joystick tasks on a daily basis. Our goal in this study was to identify the level of joystick task performance that could be maintained by 10 sec. of live, color video of a conspecific social group contingent upon the completion of a joystick task. The subjects were five individually housed bonnet macaques that were highly experienced on joystick tasks. Performance with social-video reward was compared to that maintained by a 190-mg banana-flavored pellet reward and to a nonreward condition. Comparable levels of task activity were maintained by both video and pellet reward, whereas task activity nearly ceased in the absence of reward. Four of the five monkeys increased their levels of task activity between the first and second weeks of social-video reward.

Role of Multiple-Pellet Rewards in Acquisition and Extinction of a Runway Response

4 groups of 10 rats were given continuous reinforcement training in a straight runway. All Ss received 100 pellet rewards, but groups differed in number of locomotor responses, goalbox placements, and number of pellets received on each trial. Following acquisition, Ss in each of the main groups were given massed or distributed extinction training. The results showed that Ss required to make a greater number of locomotor responses had faster terminal acquisition speeds and were more resistant to extinction. The results are discussed in terms of the Amsel, Hug, and Surtidge (1968) multiple-pellet reward hypothesis.