Academic journal article Attention, Perception and Psychophysics

The Effects of Type of Interval, Sensory Modality, Base Duration, and Psychophysical Task on the Discrimination of Brief Time Intervals

Academic journal article Attention, Perception and Psychophysics

The Effects of Type of Interval, Sensory Modality, Base Duration, and Psychophysical Task on the Discrimination of Brief Time Intervals

Article excerpt

Published online: 6 March 2014

© Psychonomic Society, Inc. 2014

Abstract The present study was designed to investigate the influences of type of psychophysical task (two-alternative forced-choice [2AFC] and reminder tasks), type of interval (filled vs. empty), sensory modality (auditory vs. visual), and base duration (ranging from 100 through 1,000 ms) on performance on duration discrimination. All of these factors were systematically varied in an experiment comprising 192 participants. This approach allowed for obtaining information not only on the general (main) effect of each factor alone, but also on the functional interplay and mutual interactions of some or all of these factors combined. Temporal sensitivity was markedly higher for auditory than for visual intervals, as well as for the reminder relative to the 2AFC task. With regard to base duration, discrimination performance deteriorated with decreasing base durations for intervals below 400 ms, whereas longer intervals were not affected. No indication emerged that overall performance on duration discrimination was influenced by the type of interval, and only two significant interactions were apparent: Base Duration × Type of Interval and Base Duration × Sensory Modality. With filled intervals, the deteriorating effect of base duration was limited to very brief base durations, not exceeding 100 ms, whereas with empty intervals, temporal discriminability was also affected for the 200-ms base duration. Similarly, the performance decrement observed with visual relative to auditory intervals increased with decreasing base durations. These findings suggest that type of task, sensory modality, and base duration represent largely independent sources of variance for performance on duration discrimination that can be accounted for by distinct nontemporal mechanisms.

Keywords Temporal processing . Filled and empty intervals . Sensorymodality . Psychophysical task

Psychophysical research on human performance on duration discrimination provides, at least to some extent, a puzzling picture of rather inconsistent results. In his comprehensive review on psychological time, Grondin (2001) suggested various structural aspects that effectively modulate estimates of timing performance as a possible cause for these ambiguous findings. The term "structural aspects" refers to the physical characteristics of an interval (see Grondin, 2001) and, thus, not only comprises the type of interval (filled vs. empty) but also aspects such as the sensory modality of the signals that mark the intervals to be compared (e.g., auditory vs. visual) and the base duration of the intervals. In this context, base duration denotes the (range of) standard durations used in a given timing study. In studies on duration discrimination, commonly employed base durations are on the order of tens to hundreds of milliseconds (see Grondin, 2010; Penney, 2003). An additional source of variance that may also account for conflicting findings in studies on duration discrimination represents the psychophysical task applied for investigating discrimination performance (see Lapid, Ulrich, & Rammsayer, 2008; Ulrich, 2010).

One major reason for the difficulties to arrive at unambiguous conclusions or, at least, to explain some of the apparently existing contradicting findings in psychophysical research on duration discrimination, represents the fact that structural aspects of the intervals to be compared differ greatly across studies, and even between experiments within a given study. In order to arrive at any definitive statement, the influence of these major structural aspects, as well as the potential influence of the psychophysical task applied, has to be taken into account. On the basis of these considerations, the present article represents a mainly empirical contribution with the objective of a concurrent, systematic assessment of the effects of the above-mentioned major structural aspects and of the psychophysical task on the discrimination of brief time intervals. …

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