Search

Forward, backward, and combined forward‐backward masking of a 1‐msec click by noise bursts were examined for N0S0 and N0Sπ stimulus configurations. The silent interval between the noise masker and the click ranged from 0 to 30 msec for forward and backward masking conditions. For combined forward‐backward masking, the silent interval between the two noise maskers ranged from 1 to 60 msec, and the click was positioned at various points within this interval. The results, which were consistent with previous reports, indicated that masking level difference (MLDs) are obtained for both forward and backward masking. The largest MLDs were obtained in the combined forward‐backward masking conditions. In both the N0S0 and N0Sπ stimulus configuration, the amount of masking in the combined forward‐backward masking conditions varied as much as 10 dB as the click was moved within the intermasker interval. The results of this study are compared with data from investigations of masking with forward and backward fringes....

Behavioral thresholds for 500, 2000, and 8000 Hz tone bursts were determined for 6‐ and 10‐month‐old human infants using a transformed up‐down tracking procedure in a conditioned head turn paradigm. In experiment 1, stimuli were presented in free field and tracking was initiated at an intensity well above threshold. For 10‐month‐old infants, threshold estimates were approximately 15 dB above adult values at all three frequencies. Six‐month‐old thresholds were slightly higher and relatively flat across frequencies. In experiment 2, stimuli were presented via earphone, tracking was initiated below threshold, and supra threshold probe trials were introduced to assess the infants' motivation to respond. With these changes in procedure, 6‐month‐olds showed the adult U‐shaped sensitivity function. [Work supported by NINCDS.]