Academic journal article Canadian Journal of Experimental Psychology

Short-Term Memory and Time Estimation: Beyond the 2-Second "Critical" Value

Academic journal article Canadian Journal of Experimental Psychology

Short-Term Memory and Time Estimation: Beyond the 2-Second "Critical" Value

Article excerpt

Abstract We showed previously that when time intervals around two seconds (s) are reproduced concurrently with a memory task, intervals are positively related to duration of memory processing. However, some data in research on timing as well as in memory research suggest that 2 s might be a critical duration beyond which different mechanisms or structures would support performance. This implies that the interference observed between memory processing and 2-s productions could be specific to these durations, and would not be obtained with longer durations. In this experiment, intervals ranging from 1.85 to 6.45 s were reproduced by participants, who were searching simultaneously for a memory probe. At all durations, reproductions were positively related to memory set size. These findings have implications with regards to previous research indicating a discontinuity around 2-3 s in time perception. They suggest in particular that the role of memory is similar in reproduction of durations around 2 s and of longer durations.

The interference between a nontemporal task and concurrent timing is probably one of the most consistent effects in the time perception literature (Brown, 1997). The interference effect has been observed with a variety of nontemporal tasks: mirror-drawing (Brown, 1985), verbal rehearsal (Miller, Hicks, & Willette, 1978), description of a visual scene (Berg, 1979), the Stroop task (Sawyer, Meyers, & Huser, 1994), and recognition memory tasks (Hicks & Brundige, 1974). These experiments usually show that concurrent nontemporal processing shortens perceived duration and that the effect is positively related to nontemporal task difficulty.

In previous studies, we investigated the effect from short-term memory processing on concurrent time production (e.g., Fortin & Breton, 1995; Fortin & Masse, 1999; Fortin & Rousseau, 1987). Overall, intervals lengthened systematically as a function of duration of memory processing interpolated in an interval produced by participants (see Fortin, 1999). For example, when Sternberg's (1966) recognition task was performed during a 2-s interval production, intervals lengthened with increasing duration of memory processing, whether its duration was varied by manipulating complexity (i.e., number of items to process) (Fortin, Rousseau, Bourque, & Kirouac, 1993) or difficulty (i.e., rate of processing per item) (Fortin & Masse, 1999) of the search task. Corresponding manipulation of complexity in visual search tasks that required attention, but no memory processing, had no effect on intervals produced concurrently (Fortin et al., 1993, Experiments 3 and 4).

We interpreted these data as a result of disruption in timing caused by memory processing. We inferred that accumulation of temporal information was disrupted, an interpretation in agreement with a pacemaker/accumulator framework (e.g., Church, 1984; Gibbon & Church, 1984). In this framework, it is assumed that pulses must be stored in an accumulator until the accumulated count is close enough to a criterion number of pulses corresponding to the target duration. The accumulator content may be transferred in working memory, for comparison with a long-term stored criterion count corresponding to some target duration in reference memory (e.g., Gibbon & Church, 1984). Disruption in timing would temporarily interrupt the accumulation process during time production. The interruption would increase the time needed to reach the criterion, thus lengthening the produced interval.

The lengthening of produced intervals with interpolated memory processing was observed when production of a single interval, for example a 2-s interval, was practiced in training sessions before introducing the memory task (e.g., Fortin & Masse, 1999). It was also observed in a reproduction task without training, where reproduction immediately followed presentation of a target interval to be reproduced, which varied from trial to trial (Fortin & Rousseau, 1998). …

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