Discrimination Training Facilitates Pigeons' Performance on One‐trial‐per‐day Delayed Matching of Key Location

Abstract

Six pigeons were tested on a one-trial-per-day variant of delayed matching of key location. In one condition, a trial began with the illumination of a pair of quasi-randomly selected pecking keys in a large 10-key test box. Pigeons' pecks to one key (the sample) were reinforced with 8-second access to grain on a variable-interval 30-second schedule, whereas pecks to the other key (the distractor) had no scheduled consequences. In the second condition, the nonreinforced distractor was not presented. In both conditions, subjects were removed from the apparatus after 15 minutes and placed in a holding cage. Subjects were subsequently replaced in the box after a delay (retention interval) of 30 seconds and were reexposed to the illuminated sample and distractor keys for 1 minute. If a pigeon made more pecks to the sample during this interval, the distractor was extinguished and subsequent pecks to the sample were reinforced on the previous schedule for an additional 15 minutes. If, however, a pigeon made more pecks to the distractor, both keys were extinguished and the subject was returned to its home cage. For all subjects, matching-to-sample accuracy was higher in the first condition. In a second experiment, the retention interval was increased to 5, 15, and 30 minutes, and then to 1, 2, 4, 8, 12, and 24 hours. Most subjects remembered the correct key location for up to 4 hours, and in one case, up to 24 hours, demonstrating a spatial-memory proficiency far better than previously reported in this species on delayed matching tasks. The results are discussed in terms of the commonly held distinction between working and reference memory.

More evidence of robust spatial associative memory in the pigeon,Columba livia

“…The present results systematically replicate the results of Willson and Wilkie (1991) and add confidence to our conclusion that discrimination training enhances retention. In the Willson and Wilkie study, pigeons remembered spatial location samples in a delayed matching-to-sample task better when the sample study period consisted of a rewarded sample-nonrewarded distractor discrimination than when the sample study period consisted ofonly a rewarded sample.…”

“…The finding that subjects perform comparably on both tasks is an important indication of the generality of the associative memory process. We have previously shown that discrimination training facilitates remembering in a delayed matching-to-sample task (Willson & Wilkie, 1991). The results of Experiment 3 show that discrimination training enhances the retention of information in the current paradigm.…”

“…It follows, then, that this memory ability should be impaired if such discriminations are not formed. Some evidence of such an effect was reported by Willson and Wilkie (1991) in a study of delayed matching of spatial location. In that study, pigeons remembered spatial location samples better when the rewarded sample and nonrewarded distractor locations were presented during the study phase of a matching trial than when only the rewarded sample was presented.…”

“…Willson & Wilkie, 1991. In successive matching to sample (SMTS; Konorski, 1959;Wasserman, 1976), a sample is presented for a brief interval, extinguishedv.and followed, after a brief retention interval, by a stimulus that either matches or does not match the sample.…”

“…In the next session, all four keys were briefly presented in order to examine the subjects' tendency to persevere to the location that had provided food in the previous session. On the basis of results reported by Willson and Wilkie (1991), it was expected that retention would be impaired by the absence of explicit discrimination training.…”