Effects of sample duration, retention interval, and passage of time in the test on pigeons’ matching-to-sample performance

Abstract

Four pigeons served as subjects in an experiment using the go/no-go delayed matching-to-sample paradigm. The go/no-go method was used because it permits the experimenter to track the time course of discriminative performance throughout the test period, unlike the conventional choice matching procedure. It was found that discriminative test performance increased with longer sample durations; performance decreased with longer retention intervals and also as time passed in the test period. The rate of forgetting was virtually the same when either the retention interval was lengthened or time elapsed in the test. These findings support a modified trace theory, which proposes that the sample stimulus trace decays at a constant rate from the point of sample offset, and that the decaying memory trace is repeatedly compared with the prevailing test stimulus as time passes in the test period.The delayed matching-to-sample (DMTS) procedure has been used extensively to study animal short-term memory. In this conditional discrimination procedure, a sample stimulus is presented for a specified period of time, after which a delay or retention interval is imposed, followed by presentation of one or more test stimuli. In the choice DMTS procedure, two or more test stimuli are presented and the subject must select the stimulus that matches the prior sample in order to earn reinforcement (Blough, 1959). Another kind of DMTS procedure involves presentation of only one test stimulus at a time. If the test stimulus matches the prior sample, reinforcement is scheduled; however, if the test stimulus does not match the sample, no reinforcement is delivered. The subject's "choice" here is whether or not to respond (Konorski, 1959;Wasserman, 1976). This second method can be called go/no-go DMTS.In the typical choice DMTS procedure, the test stimuli offset as soon as a response is made, whereas in the go/no-go task, the test stimulus may remain on for longer periods of time. Having the test stimulus stay on beyond the first response permits an evaluation of subjects' response rates. Wasserman (1976), for example, found that pigeons responded differentially on matching and nonmatching trials, with overall response rates higher on matching trials. The mean latencies to the first test keyThis research is based on the first author's thesis, submitted to the University of Iowa in partial fulfillment of the requirements for the MA degree. The authors wish to thank Dan Neunaber, Gary Schroeder, and Diane Chatlosh for their help with this project. The comments of the Editor and two anonymous reviewers were also of considerable value to the preparation of this report. Requests for reprints should be sent to E. A. Wasserman.

Delayed Matching‐to‐sample Performance of Hens: Effects of Sample Duration and Response Requirements During the Sample

“…Prior studies with species other than chickens have demonstrated that DMTS accuracy improves when either sample durations or sample-key response requirements increase (e.g., Farthing et al, 1977;Grant, 1976;Guttenberger & Wasserman, 1985;Leith & Maki, 1975;Lydersen et al, 1977;Maki, Gillund, Hauge, & Siders, 1977;Maki, Moe, & Bierley, 1977;Nelson & Wasserman, 1978;Roberts, 1972;Roberts & Grant, 1974;Roberts & Kramer, 1982;Shimp & Moffitt, 1977;White, 1985). Similar findings were reproduced with chickens in the present study.…”

“…It has been suggested that trace strength is a positive function of sample duration and a negative function of time since sample offset (Guttenberger & Wasserman, 1985;Roberts, 1972;Spetch & Treit, 1986).…”

“…For example, Roberts (1972) and Roberts and Grant (1976) proposed that DMTS performance is the result of comparisons of the test stimuli with a gradually decaying internal analogue (trace) of the sample stimulus. It has been suggested that trace strength is a positive function of sample duration and a negative function of time since sample offset (Guttenberger & Wasserman, 1985;Roberts, 1972;Spetch & Treit, 1986).…”

“…Increasing the duration of sample-stimulus presentations also increases accuracy under DMTS procedures (e.g., Farthing, Wagner, Gilmour, & Waxman, 1977;Grant, 1976;Guttenberger & Wasserman, 1985; Leith & Maki, 1975;Nelson & Wasserman, 1978;Roberts & Grant, 1974;Shimp & Moffitt, 1977 sample-key response requirements are, however, characteristically confounded in studies ostensibly concerned with either variable alone. In studies of response requirements, the duration of the sample stimulus characteristically is determined by the time required to complete the programmed ratio.…”

Writing and overwriting short-term memory

“…Memory for stimuli decreases both during their retention and during their recall (Guttenberger & Wasserman, 1985). A compound model provides a good treatment of both forgetting functions (Figures 2-4) and acquisition functions (Figure 9).…”