One Bar‐press Per Day: Acquisition and Extinction

Abstract

Ordinarily, when a learned response is no longer followed by reward, the probability of the occurrence of this response is diminished and ultimately the response is extinguished. The present study explores the possibility of preventing the extinction of a bar-pressing response under one-trial-a-day acquisition and one-trial-aday extinction when the bar is always removed immediately after it has been pressed.EXPERIMENT I SubjectsThe Ss were 16 naive female hooded rats, 80-90 days old at the beginning of the experiment, from the colony of the Psychology Department of Michigan State University. The animals served as Ss for extended periods, in one case as long as 6 months. Apparatus A very simple b-ar-pressing apparatus was used. The box was a plywood 10-inch cube with a 5-by-7-inch glass window on the side opposide the bar. The top was covered with hardware cloth through which the rat was observed. The cylindrically shaped bar was 6 millimeters in diameter, located midway in one wall 2 inches above the floor. The bar extended 2 1/2 inches into the box and a 10-gram pressure was required to depress it. A metal food tray was located on the floor 1 inch to the right of the bar. Following an excursion of 1/4 inch or more of the bar, as determined by the release of a pendulum on the outside of the box, a pellet of food (approximately 0.05 gram) was dropped manually through a short metal tube into the food tray. The bar could be immediately retracted by a simple manual movement. Preliminary training Five days of handling and being on a reduced diet were followed by six days of preliminary training. Once a day during this period each S was placed, two at a time, in a box with the bar removed. The food tray contained 20 pellets and each pair of rats remained in the box until all the pellets were consumed. The pairings differed randomly from day to day. Throughout this period and the remainder of the experiment the Ss were fed 9 grams of food 5-10 minutes after being removed from the box. A variety of experimentation in our laboratory indicates that this interval is sufficiently long to prevent incidental reinforcement of a prior response. TrainingThere were two main groups of subjects, the control (N = 6) and the experimental (N = 10). Two additional animals were discarded, one from each main group, because they failed to press the bar within 5 minutes on five successive days. The experimental -Ss were divided into two sub-groups, E -10 (N = 5) and 81

Prolonged extinction following one session of food-reinforced conditioning: A methodological note.

“…Although the failure to observe any trend toward lower scores as extinction proceeded is somewhat supportive of the second interpretation, confident selection between these interpretations must await further research. Denny (1959) has recently reported a somewhat similar result. He found no evidence of extinction, defined as a lengthening in the latency of bar pressing, in animals given access to a bar for only 1 unreinforced bar press per day for 75 days, following limited conditioning with a food reinforcer.…”

Common Processes May Contribute to Extinction and Habituation

“…Extinction may also occur when only one trial is given per day (Table 1, Characteristic 79; but see also Denny, 1959). One possible explanation for this finding is that long-term habituation accumulates with successive stimulus exposures and survives the lengthy time between trials.…”

Runway performance of goldfish as a function of complete and incomplete reduction in amount of reward

“…The possibility should be considered, however, that the failure of the fish to show the depression effect was the product simply of a set of conditions under which the effect might also fail to appear in rats. Denny (1959), for example, found that rats trained in a leverpressing situation at the rate of one trial per day showed no deterioration whatsoever in *This work, done at Bryn Mawr College, was supported by Grants 02857 and 15902 from NIMH. Requests for reprints should be sent to R. C. Gonzalez, Department of Psychology, Bryn Mawr College, Bryn Mawr, Pa. 19010.…”