Some Time Violations Go Less Noticed: Gestalt Grouping? A Brief Report

Abstract

This brief report is inspired by Bolton’s (1894, Am. J. Psychol., 6, 145–238) tick-tock phenomenon, which describes an illusionary accented grouping of isochronous, non-accented click sequences. It has repeatedly been shown that in stimulus-wise grouped sequences of an XXXOOO character (where X differs from O in terms of intensity, pitch level, or filled or unfilled duration), gap deviations between groups are more prone to go unnoticed compared to deviations within a group (e.g., Fitzgibbons et al., 1974, Percept. Psychophys., 16, 522–528.). Yet, not much is known about whether comparable anisochrony insensitivities might also occur in equal-accented sequences (XXXXX). In a same/different task setting, listeners had to detect isochrony deviations that appeared in different empty-interval locations across 800 trials within a five-pulse sequence of 250 ms interonset intervals. Findings revealed a major location dependency, with least detection accuracy for gap deviations occurring in the last interval, particularly if the 250 ms gap was lengthened rather than shortened. Results are discussed in relation to potential Gestalt grouping and Nakajima et al.’s (2014, Perception, 33, 1061–1079) perceptual assimilation and contrast observations in three-tone sequences.