Lipreading and audiovisual speech recognition across the adult lifespan: Implications for audiovisual integration

Abstract

In this study of visual (V-only) and audiovisual (AV) speech recognition in adults aged 22-92 years, the rate of age-related decrease in V-only performance was more than twice that in AV performance. Both auditory-only (A-only) and V-only performance were significant predictors of AV speech recognition, but age did not account for additional (unique) variance. Blurring the visual speech signal decreased speech recognition, and in AV conditions involving stimuli associated with equivalent unimodal performance for each participant, speech recognition remained constant from 22 to 92 years of age. Finally, principal components analysis revealed separate visual and auditory factors, but no evidence of an AV integration factor. Taken together, these results suggest that the benefit that comes from being able to see as well as hear a talker remains constant throughout adulthood and that changes in this AV advantage are entirely driven by age-related changes in unimodal visual and auditory speech recognition. (PsycINFO Database Record

Figure 1

Photographs illustrating the five levels of blur used in the present investigation. A Snellen Eye Chart is included for comparison.

Figure 2

V-only and AV speech recognition as a function of the clarity of the visual speech signal. The left panel shows mean performance for each age group in the five V-only conditions, and the right panel shows mean performance for each group in the five corresponding AV conditions. In both panels, the error bars indicate the standard error of the mean.

Figure 3

Individual participants’ speech recognition in the A-only condition as well as in the V-only and AV conditions with no blurring of the visual speech signal. Each participant’s performance in the three conditions is plotted as a function of that participant’s age.

Figure 4

Individual participants’ speech recognition in the A-only condition and in the blur condition in which their V-only performance was closest to 30% words correct, as well as in the AV condition with the corresponding SNR and blur. Each participant’s performance in the three conditions is plotted as a function of that participant’s age.

Figure 5

Individual participants’ AV speech recognition as a function of the sum of their speech recognition scores in the V-only and A-only conditions. Data are replotted from Figure 4 so as to illustrate the super-additive effect resulting from adding the visual speech signal to the auditory signal. Points above the diagonal represent data from participants who showed super-additive effects.