Delayed Stream Segregation in Older Adults: More Than Just Informational Masking.

ABSTRACT

OBJECTIVE: To determine whether the time course for the buildup of auditory stream segregation differs between younger and older adults. DESIGN: Word recognition thresholds were determined for the first and last keywords in semantically anomalous but syntactically correct sentences (e.g., "A rose could paint a fish") when the target sentences were masked by speech-spectrum noise, 3-band vocoded speech, 16-band vocoded speech, intact and colocated speech, and intact and spatially separated speech. A significant reduction in thresholds from the first to the last keyword was interpreted as indicating that stream segregation improved with time. RESULTS: The buildup of stream segregation is slowed for both age groups when the masker is intact, colocated speech. CONCLUSIONS: Older adults are more disadvantaged; for them, stream segregation is also slowed even when a speech masker is spatially separated, conveys little meaning (3-band vocoding), and vocal fine structure cues are impoverished but envelope cues remain available (16-band vocoding).