Specificity of learning in an auditory temporal‐order task

The ability to determine the onset order of two tones at different frequencies is a measure of temporal acuity and an analog of voice‐onset time. Learning in this temporal‐order task and its generalization to untrained frequencies and temporal‐acuity tasks was explored. Temporal‐order thresholds of six listeners trained 1 h per day for 6 days with tones at 0.25 and 4 kHz improved from 58 ms before to 12 ms after training, yielding a proportional improvement greater than on all untrained conditions. Comparisons between proportional improvements of trained and control listeners revealed that trained listeners learned considerably more than controls on the trained condition, and only slightly or no more than controls on: (1) the trained task at two sets of untrained frequencies (0.5 and 1.5 kHz, 0.75 and 1.25 kHz), and (2) three untrained temporal‐acuity tasks (offset temporal order, onset asynchrony, offset asynchrony) at the trained frequencies. The lack of robust generalization to untrained frequencies and tasks suggests learning in onset temporal‐order tasks is mediated by a frequency‐dependent mechanism different from the mechanism(s) underlying performance in other temporal‐acuity tasks. By increasing our understanding of plasticity in temporal‐acuity mechanisms, these data may guide the treatment of related disorders. [Work supported by NIDCD.]