Lynne A. Werner
Lisa R. Mancl
Janelle Constantino
Dept. Speech and Hear. Sci., CDMRC, WJ-10, Box 47, Univ. of Washington, Seattle, WA 98195
In a previous study [L. A. Werner et al., Child Devel. 63, 260--272 (1992)], it was found that human infants are very bad at detecting gaps in broadband noise, with gap detection thresholds of about 50 ms. An adaptive method was used to estimate thresholds. Here, d' is estimated in blocks of 30 trials at a fixed gap duration (ranging from 5 to 70 ms) and a psychometric function is constructed for each infant to estimate the gap detection threshold. A 30-dB spectrum level noise was presented continuously. On signal trials, a series of 12 gaps, 500 ms apart occurred; on no-signal trials, the noise continued uninterrupted. An observer-based method was used to test the infants. Three- and six-month-old infants were tested. Infants' psychometric functions for gap detection were quite variable in slope: some infants had functions with ranges of about 10 ms, while a few infants had ranges of 30 ms. As in the previous work, infant thresholds remained quite poor; there was little change in threshold between 3 and 6 months of age. [Work supported by NIH.]