Effects of signaled retention intervals on pigeon short-term memory

Abstract

In three delayed matching-to-sample experiments, pigeons were given distinctive stimuli that were either correlated or uncorrelated with the scheduled retention intervals. Experiment 1 employeda single-key, go/ncrgo matching procedure with colors as the sample and test stimuli; lines of differing orientations signaled short or long delays for one group, whereas the lines and the delays were uncorrelated for the other group. The function relating discriminative test performance to delay length was steeper in the correlated group than in the uncorrelated group. In addition, the line orientation stimuli controlled differential rates of sample responding in the correlated group, but not in the uncorrelated group. In Experiment 2, subjects extensively trained with correlated line orientations were exposed to reversed cues on probe trials. Miscuing decreased discriminative test responding at the short delay, but enhanced it at the long delay. As in the correlated group of the first experiment, rates of sample keypecking were higher in the presence of the "short" time tag than in the presence of the "long" time tag. Experiment 3 used a three-key choice-matching procedure and a withinsubjects design, and equated reinforcement rate at the short and long delays. When auditory stimuli were correlated with delay length, the function relating choice accuracy to delay was steeper than when the stimuli and the delays were uncorrelated. The consistent effects of signaled retention intervals on memory performance may be understood in terms of differential attention to the sample stimuli.Recently, the delayed matching-to-sample paradigm (e.g., Blough, 1959) and its numerous procedural variants (e.g., Shimp & Moffitt, 1977;Wasserman, 1976) have been used to investigate short-term memory in nonhuman subjects. Many of these studies of animal short-term memory have scheduled several different retention intervals during daily sessions, with the time values varying randomly and unpredictably from trial to trial.An exception to this practice was an experiment by Perkins, Lydersen, and Beaman (1973). There, pigeons were given stimuli that indicated not only which comparison stimulus to select at test, but also how long it would be until the memory test would be administered. These subjects showed generally better discrimination at 2-, 4-, and 6-sec retention intervals than other birds given the same delays, but nondifferentially associated with the sample stimuli.These results are consistent with the proposal that information about the upcoming retention interval facilitates memory of the sample stimulus. Unfortunately, another equally plausible hypothesis can explain the results: Because they were consistently associated with the sample stimuli, the specific delay interval durations themselves could also have served as discriminative stimuli controlling test responding for the first group of subjects but not the second, thereby supporting superior discriminative responding (Stubbs, 1968).The present study explored the influence of reten...

Memory interval distribution effects in pigeons

“…It could be tested by separating the cues for the correct discriminative response from the cues for the MI duration. This strategy was used by Wasserman, Grosch, and Nevin (1982) and more recently by MacDonald and Grant (in press). The latter authors signaled the duration of either a long or a short MI on each trial in delayed matching with pigeons.…”

“…This method would be similar to the procedure used by Wasserman et al (1982) and by Dodd and Honig (1981) to signal specific memory intervals. A single set of initial stimuli would control the conditional discrimination.…”

“…It may be useful to recall the study by Wasserman et al (1982) in this connection. In some phases of their work, they presented cues that were correlated with the MI.…”

“…This effect has been studied much less extensively than the differential outcomes effect or directed forgetting. Wasserman, Grosch, and Nevin (1982) have provided a clear example. In two experiments, they trained pigeons on a delayed conditional discrimination, in which orange and green served as the initial stimuli and as the singly presented test stimuli.…”

Prospective representation: The effects of varied mapping of sample stimuli to comparison stimuli and differential trial outcomes on pigeons’ working memory

“…The basic distinction is whether working memory contains a representation of "what the animal has seen" or a representation of "what the animal anticipates responding to" (Honig & Riley, Cook, & Lamb, 1981;Roitblat, 1982;Stonebraker, 1981). In favor of the prospective position, the results of several studies have suggestedthat pigeons performing in delayed matching tasks actively anticipate response decisions (Honig & Dodd, 1983;Honig & Wasserman, 1981), trial outcomes (Edwards, Jagielo, Zentall, & Hogan, 1982;Honig, Mathe-son & Dodd, 1984;Peterson, 1984;, and the duration of memory intervals (Dodd & Honig, 1981;Wasserman, Grosch, & Nevin, 1982).…”