ASA 125th Meeting Ottawa 1993 May

4aPP6. Pure-tone thresholds of 1-month-old infants.

Lynne A. Werner

Lisa Rickard Mancl

Dept. Speech and Hear. Sci., Univ. of Washington, WJ-10, Seattle, WA 98195

Thresholds for the detection of tones at 0.5, 1, and 4 kHz were estimated for 1-month-old infants using insert earphones. On each trial, the infant was presented with either 8 repetitions of a tone burst or with no sound for an 8-s period.Based on the infant's response, an observer, blind to trial type, gave a confidence rating at the end of each trial. Correct infant responses were reinforced. The level and frequency of the tone were fixed within a session; several sessions, at different levels, were completed for each subject. The confidence ratings were used to calculate p(A). Performance for a session was taken as the highest p(A) achieved in a block of 8 trials. Thresholds were calculated as the level at which p(A)=0.83, where 0.83 just exceeds chance for 8 trials. Thresholds were calculated for infants who achieved p(A)(greater than or equal to)0.83 in at least one session and who had monotonic psychometric functions. The results were in close agreement with previous studies and suggest that 1-month-old infants are more sensitive at lower frequencies. The current procedure uses fewer trials to estimate a threshold and allows thresholds to be estimated for a higher proportion of the infants tested. [Work supported by NIH.]