Effects of sample duration and spaced repetition upon delayed matching-to-sample in monkeys (Macaca arctoides andSaimiri sciureus)

Two rhesus monkeys were tested in 6-and Iü-item list memory tasks for performance changes as a function ofthe exposure duration ofthe list stimuli and the interstimulus interval (lSI) between successive list stimuli. Accuracy increased with longer item exposure duration and tended to decrease with longer ISI duration. Humans, by contrast, typically show increases in accuracy with ISI, a result taken as evidence of rehearsal. The decrease in accuracy for monkeys suggests that they were not using rehearsal processes in these list memory experiments. Further tests in which choice accuracy with predictahle ISls was compared with choice accuracy with unpredictahle ISls also yielded no evidence of rehearsal by the monkeys. This apparent absence of rehearsal mechanisms in monkeys, in situations also shown to support human rehearsal, is discussed as a potential difference in the visual working memory processes of the two species.Humans regularly engage in rehearsal. Indeed it is difficult to imagine a day going by without our rehearsing something, whether it be telephone numbers, addresses, shopping lists, or names of new acquaintances. Although rehearsal often involves language, this apparently is not a necessary requirement; rehearsal can occur with pictorial stimuli in humans (Watkins, Peynircioglu, & Brems, 1984). In this article, rehearsal will be considered as a subject-controlled, memory-based repetition of to-be-remembered material (cf. Johnson, 1980;Watkins & Peynircioglu, 1982). This relatively broad view of rehearsal includes both the overt and covert rehearsal of either visual or verbal materials. When considered thus, rehearsal does not depend on language, and this opens up the possibility that other animals may also have rehearsal-like processes. Procedures involving our human capabilities for language and speech have been valuable and frequently used in the study of rehearsal (see, e.g., Dark & Loftus, 1976;Rundus, 1971;Rundus & Atkinson, 1970; Modigliani & Hedges, 1987), but obviously they cannot be used in examining this question in other animals.During the past decade, the interstirnulus-interval (181) or blank-time procedure has been developed as a promising means of studying animal rehearsal. Rehearsal in humans is identified in this procedure through the increased accuracy that is observed when the ISls between the iterns of a to-be-remembered list or sequence are lengthened. 153For example, Intraub (1980) presented subjects with sequences of 16 pictures at different ISls and then tested item recognition. Subjects presented with pictures for l l O msec and no ISI performed at only 59 % accuracy, but as the ISI was lengthened to 385 msec, 620 msec, 1,390 msec, and finally 4,890 msec, performance increased to 71 %, 78 %, 91 %, and 92 %, respectively. 1 Performance in the 4,89O-msec ISI condition (viewing time, 110 msec) was as accurate as it was when each item was visible for 5 sec. This increase in accuracy with langer ISls will be referred to as the ISI effect in the present article.The ISI effect...

Section: Discussioncontrasting

confidence: 56%

contrasting

confidence: 55%

Interstimulus interval and viewing time effects in monkey list memory

Cook

Wright

Sands

1991

“…This suggests that the visual element was largely ignored in favor of the auditory element. Experiments with pigeons (Grant, 1976)and monkeys (Herzog et al, 1977) have shownthat decreasedpresentation time of the (visual) sample results in decreased levels of performance. When monkeys (but not pigeons) are givenextensive experience with short sample durations, the deleteriouseffect of decreasing durations can be eventuallyovercome.…”

Section: Discussionmentioning

confidence: 99%

“…Then the visual element was reduced in duration while the auditory element was held constant. Changes in sample duration have been found to influence matching performance in pigeons (Maki & Leith, 1973;Nelson & Wasserman, 1978;Roitblat, 1980), monkeys (Devine, Jones, Neville, & Sakai, 1977;Herzog, Grant, & Roberts, 1977), and dolphins (Herman & Gordon, 1974).…”

Section: Part Bmentioning

confidence: 99%

Delayed matching of visual materials by a bottlenosed dolphin aided by auditory symbols

Forestell

Herman

1988

A bottlenosed dolphin (Tursiops truncatus) with good underwater and aerial visual acuity was tested in visual matching-to-sample (MTS) paradigms. Attempts to train visual identity MTS directly, using two simple two-dimensional patterns as sample stimuli and as alternatives (comparison stimuli), met with little success, in keeping with previously observed difficulties of this auditory-specialized species for learning complex tasks utilizing simple visual materials. Pairing of each visual sample with a unique sound, to produce a compound auditory-visual sample, while retaining the two visual alternatives, resulted in the dolphin's learning both auditory-visual symbolic matching and visual-visual identity matching. At O-sec delay, performance with the auditory element of the sample alone was equivalent (76%) to performance with the visual element alone; performance with the compound was distinctly better (95%-98% correct). Testing with longer delays using the visual element alone resulted in successful matching through to a maximum delay of 34 sec. These results provided the first demonstration of delayed MTS in a dolphin using visual materials, and complemented other data showing the ready capability of this species for delayed auditory MTS. It appeared that the dolphin solved the visual MTS task by forming auditory codes to represent the visual materials, and that these auditory codes were eventually replaced with purely visual codes.Delayed-matching-to-sample (DMTS) tasks have been used extensively in the analysis of animal memory (Roitblat, 1982). In the typical form of these tasks, a to-beremembered stimulus (the sample) is presented briefly. The animal then indicates its memory for the sample by choosing a matching stimulus from among subsequently offered alternatives. In identity matching, the correct alternative physically matches the sample. In symbolic matching, the alternatives are learned associates of the samples (e.g., D 'Amato & Worsham, 1974;Herman & Thompson, 1982;Roitblat, 1980). For example, a red disk, shownas a sample, may be symbolically represented among the alternatives by an inverted triangle.With rare exceptions, the stimuliused in matchingtests have been limitedto the single,dominantsensorymodality for the species studied. The reason is straightforward: it has proven extremely difficult to teach any animal a DMTS task when task information is given other than through its presumed major sensory interface with its environment. For the pigeon and nonhuman primate, this has been vision. If both sample and alternativesare visual stimuli (visual-visual, or V-V, matching), DMTS is relatively easy to teach these animals (e.g.,

“…The present experiment differed from Medin's (1974) earlier experiment along a number of variables, such as number of sample presentations, length of delay intervals, and whether or not the sample presentations were invariably rewarded. One idea suggested by Herzog et al (1977) is that the advantage of spaced presentations derives from differential encoding on the two appearances of the sample. One may speculate that, after several additional years of experience, the monkeys become less variable in their encoding of stimuli so that variability in encoding did not increase with lSI.…”

Section: Methodsmentioning

confidence: 99%

Proactive interference in monkeys: Delay and intersample interval effects are noncomparable

Medin

1980

Two prominent theories of proactive interference in animal memory predict that the effects of varying the interval between the interfering and to-be-remembered stimulus in a delayedmatching-to-sample paradigm ought to be comparable to the effects of manipulating the retention interval. To assess this prediction, monkeys were tested in a situation in which a sample was presented, followed by a variable intersample interval, whereupon a second sample was presented. After a delay interval, a choice test was given between the two stimuli that had served as samples. The correct choice was always the most recently presented sample stimulus, and the initial sample of a sequence provided a potential source of proactive interference. In two experiments, delay interval altered performance, whereas interstimulus interval had little or no effect. In a third experiment, using a small set of sample stimuli, intertrial interval altered proactive interference, but again interstimulus interval had no effect. One way of accounting for these data is in terms of distinct short-and long-term memory processes. 553As interest in short-term memory in animals continues, the number of stable empirical relationships uncovered steadily mounts. There is evidence, for example, that interference treatments alter memory for stimuli, responses, and reinforcers in a similar way (Maki, Moe, & Bierley, 1977) and produce the same pattern of results regardless of whether the subject population consists of pigeons, monkeys, or dolphins (D'Amato,1973;Herman, 1975;Roberts & Grant, 1976;Wilson, 1974;Worsham, 1975;Zentall & Hogan, 1974). Not surprisingly, there has been a concomitant interest in theories of animal memory, especially as they apply to interference phenomena.In discussing contrasting theories it will be useful to focus on a concrete experimental situation. Consider a delayed-matching-to-sample (DMTS) paradigm with two kinds of trials: (1) control trials, in which sample stimulus B is presented and, after a delay (retention) interval, a choice between stimulus A and stimulus B is given, with stimulus B rewarded; or (2) proactive interference trials, in which stimulus A is presented, then stimulus B is presented, and, after a delay interval, A and B are given on the choice test with stimulus B rewarded. Over an experimental session, A and B are rewarded equally often so that the correct solution is to choose the stimulus that has most recently served as a sample. Typically, performance on control trials surpasses that on inter- ference trials. Any memory theory must be able to address this basic finding.Although this paradigm seems to provide a natural tool for examining relationships between short-and long-term memory, the two most prominent theories of DMTS (D'Amato, 1973;Roberts & Grant, 1976) do not assume that performance reflects separate contributions from short-and long-term memory. Roberts and Grant, for example, proposed that longterm memory does not enter into pigeon DMTS performance. Instead, they assume that performance is contro...