This study was designed to examine whether age-related differences in melodic pitch perception may be mediated by temporal processing. Temporal models of pitch suggest that performance will decline as the lowest component of a complex tone increases in frequency, regardless of age. In addition, if there are age-related deficits in temporal processing in older adults, this group may have reduced performance relative to younger adults even in the most favorable conditions.
Six younger adults and 10 older adults with clinically normal audiograms up to 8 kHz were tested in a melodic pitch perception task. In each trial, two consecutive four-note melodies were presented to the listener. Melodies were identical with the exception of one note in the second melody that was shifted in pitch. The listener was required to identify which note was shifted. All notes consisted of eight successive harmonic components, with the average lowest component manipulated to be the 4th, 8th, or 12th component of the harmonic series, with lower components being absent.
Age-related differences in melodic pitch perception were only apparent when stimulus parameters favored temporal processing of pitch. Furthermore, modeling a loss of periodicity coding yielded an outcome consistent with the observed behavioral results. Although younger adults generally outperformed older adults, about one-quarter of the older adults performed at levels that were equivalent to those of younger adults. The only follow-up tests that were able to differentiate these exceptional older adults were tests that would be sensitive to temporal processing: Fundamental frequency difference limens and 500 Hz pure-tone difference limens. In contrast, otoacoustic emissions and high-frequency pure-tone thresholds, which are more commonly associated with spectral processing deficits, were not able to differentiate older exceptional adults from older typical adults.
Age-related declines in temporal processing contribute to deficits in melodic pitch perception. However, some exceptional older adults with normal audiograms preserve excellent temporal processing and continue to perform at levels that are typical of younger adults.