Asynchronous vowel-pair identification across the adult life span for monaural and dichotic presentations

Temporal order abilities decrease with age. Declining temporal processing abilities may influence the identification of rapid vowel sequences. Identification patterns for asynchronous vowel pairs were explored across the life span.

Young, middle-aged, and older listeners completed temporal order tasks for pairs of 70-ms and 40-ms vowel stimuli. For a given vowel duration, naturally spoken vowels were equated for duration, intensity, and fundamental frequency. Listeners completed monaural and dichotic temporal order tasks that involved identifying the vowel pair in the correct order. The stimulus onset asynchrony that yielded 50% accuracy for identifying the vowel pair in the correct order was used to equate performance among listeners. Vowel identification response patterns were determined at this stimulus onset asynchrony threshold.

Vowel identification patterns were largely consistent across age groups. Older listeners were influenced by the order of certain vowel pairs. Not all vowel pairs were identified equally well. Vowel dominance patterns were also observed, with /a/ being identified most accurately for the vowel pairs tested. Formant dynamics explained, in part, identification and confusion patterns.

Vowel identification accuracy patterns were reasonably similar across the life span, regardless of presentation mode, vowel duration, or effect of considerable stimulus exposure. Large effects of vowel order were observed, particularly for older listeners.