Academic journal article Attention, Perception and Psychophysics

Differences in Duration Discrimination of Filled and Empty Auditory Intervals as a Function of Base Duration

Academic journal article Attention, Perception and Psychophysics

Differences in Duration Discrimination of Filled and Empty Auditory Intervals as a Function of Base Duration

Article excerpt

In the present experiments, participants were presented with two time intervals that were marked by auditory signals, and their task was to decide which of the two was longer in duration. In Experiment 1, the base durations were 50 and 1,000 msec, whereas in Experiment 2, seven different base durations ranging from 50 to 1,000 msec were employed. It was found that filled intervals (continuous tones) were discriminated more accurately than empty intervals (with onset and offset marked by clicks) at the 50-msec base duration, whereas no performance differences could be shown for longer ones. The findings are consistent with the notion of a unitary timing mechanism that governs the timing of both filled and empty auditory intervals, independent of base durations. A likely conceptual framework that could explain better performance with filled as compared with empty intervals represents an information-processing model of interval timing that evolved from scalar timing theory. According to this account, a performance decrement observed with empty intervals may be due to a misassignment of pulses generated by an internal pacemaker.

In psychophysical studies on duration discrimination, basically two types of intervals are used (cf. Woodrow, 1951). One type is the filled interval, and the other type is the empty interval. In filled intervals, a signal is presented continuously throughout the interval, whereas in empty intervals, only the onset and the offset of the interval are marked by a brief sensory event. Thus, an empty interval is a silent duration with no signal present during the interval itself. In the literature, a highly puzzling picture of rather inconsistent findings arises with regard to the question of how the type of interval affects performance on duration discrimination. As will be discussed in more detail below, some studies found better performance on duration discrimination with filled than with empty intervals, whereas other studies reported the opposite effect or failed to reveal any differences at all. Because of the large number of highly ambiguous results, in his comprehensive reviews of the influence of filled and empty intervals on performance on duration discrimination in humans, Grondin (2001, 2003) arrived at the conclusion that, to date, no definitive statement on this issue can be made. Most interestingly, similarly inconclusive results have been reported from animal studies (e.g., Kraemer, Randall, & Brown, 1997; MacInnis, 2007; Miki & Santi, 2005; Santi, Keough, Gagne, & van Rooyen, 2007; Santi, Miki, Hornyak, & Eidse, 2006). At this point, it seems that differences in duration discrimination with filled and empty intervals may depend on various factors, such as the duration of the intervals to be compared, the sensory modality in which the intervals are presented, the physical characteristics of the markers defining the empty intervals, or the psychophysical procedure applied (cf. Allan, 1979; Fraisse, 1978; Grondin, 2001, 2003, 2008).

Another question at issue when comparing performance on duration discrimination with filled and empty intervals refers to the definition of the duration of an empty interval. When comparing filled and empty intervals, the researcher is faced with the problem of appropriately equating the physical duration of both types of intervals. In the case of a filled interval, the physical duration is directly reflected by the presentation time of the sensory signal. There is some disagreement, however, with regard to empty intervals. On the basis of the outcome of his studies on the perceived duration of empty auditory intervals in the subsecond range, Woodrow (1928) concluded that "It is entirely impossible to listen to the interval without also paying some attention to the limiting sounds. One's reaction is to some extent always a reaction to the temporal form as a whole" (p. 192). More recently, Grondin, Ivry, Franz, Perreault, and Metthé (1996) also reported longer perceived duration with empty intervals in the subsecond range marked by a 100-msec onset and a 5-msec offset marker, as compared with empty intervals bounded by 5-msec onset and offset markers. …

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