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

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).