Comprehension of Speeded Discourse by Younger and Older Listeners

Abstract

Researchers have argued that older adults are more adversely affected by speeding speech than are younger adults. However, the age effects usually occur when (1) the speech materials are artificially speeded to rates well above those that occur in natural speech; (2) the speeding method introduces distortions that tax the older adult's auditory processes; and (3) the speech materials are simple sentences or very short passages. This study evaluated whether older adults are disadvantaged when listening to extended discourse (10- to 15-min lectures) speeded to a rate near to the limit of normally encountered fast speech (240 words/min) with a minimum of acoustic distortion. Perceptual difficulty was further manipulated by presenting stimuli in either quiet or with a 12-talker background babble. Younger and older adults had more difficulty recalling the details of the discourse and integrating their contexts when stimuli were presented at faster rates and in higher levels of background noise. Although each of these manipulations were found to cause large differences in performance, the age groups were generally found to perform analogously in most conditions. Potentially the availability of semantically rich materials, and the extended durations of the passages, allowed the older adults an opportunity to adjust to the faster speech rates and maintain performance levels similar to younger adults.

This research was supported by grants from the Canadian Institutes of Health Research, the Natural Sciences and Engineering Research Council of Canada, and the National Institute on Aging. The authors thank Jane Carey and Alham Chelehmalzadah for assistance in conducting these experiments. The authors also would like to thank Hong Gao and Stan O'Brien for their help in preparing the stimuli, and James Qi for his work designing the stimulus delivery program. The authors thank Dr. Jeffrey Elias and two anonymous reviewers for thoughtful commentary on this work.

Notes

¹The most frequently used method for speeding speech artificially (e.g., Wingfield et al., 1985), divides the speech into consecutive short periods of time (e.g., 10 ms), eliminates every second, third, or fourth segment, and then closes these gaps. This method increases speed without a frequency shift, but removes speech segments without regard to their informational content. For example, if 10-ms segments are removed during a formant glide, discontinuities are introduced into the glide, and glide rate is increased. If segments are removed during a stop consonant, the duration of the stop is shortened. Such removals may affect which phoneme is heard.

Note. Values are given in Pearson correlations.

∗p < .05; ∗∗p < .01.

²Available from the authors are data comparing the performance of the older and younger adults on the cognitive tests for the current sample relative to cognitive performance in previous samples collected over the past 8 years.