Duration illusion and auditory grouping in infancy.

Bull, 1988). Infants detection of temporal increments to silent intervals between groups of tones was compared with their detection of comparable silent increments within groups of tones. Ss were presented with standard 6-tone sequences, with the fust 3 tones differing from the last 3 in harmonic structure, frequency, or intensity, and contrasting sequences with increments of 80 or 100 ms to the silent interval between the 3rd and 4th tone (XXX OOO, between groups) or between the 4th and 5th tone (XXXO OO, within group). Infants discriminated temporally altered sequences from the standard only when the increments occurred within a group. The authors conclude that perceptual grouping processes are operative in infancy and that infants perceive the silent increments between groups of sounds as longer than identical intervals within a group, as do adults. In the visual domain, illusions have traditionally been re-garded as mistakes made by the perceptual system. This is re-flected in the terminology applied to such perception, such as deficient perception (Gibson, 1966, chap. 14) and misper-ception (Hochberg, 1981, p. 257), and in the observation that perception can go wrong* * (Gregory, 1972, p. 131). In the re-