The effects of semantic predictability in non-pathological older adults' production of a phonemic contrast

The present study examined the effects of semantic predictability in non-pathological older adults' production of the /t/-/d/ phonemic voice contrast. Experiment 1 examined young and older adults' production of /t/ and /d/ words embedded in semantically biasing and neutral passages and when produced in the clear or in noise. Experiment 2 assessed the perceptual intelligibility of subjects' production by examining listeners' identification of the /t/-/d/ words produced in Experiment 1. The results replicate previous findings demonstrating that duration lengthens in neutral vs. biasing contexts. However, the results also show agerelated differences. Older adults preserved the /t/-/d/ contrast in all the experimental manipulations; young adults were more variable. In addition, listeners were better able to identify the words produced by the older adults. We suggest that older adults compensate pragmatically for their cognitive inability to integrate and process the semantic information in the neutral contexts. Consequently, they adopt a strategy for all passages and hyperarticulate the /t/-/d/ contrast in an attempt to ensure successful communication. It is believed that these results contribute to the understanding of the normal ageing process in speech production, and may help identify differences between normal life-span developments and pathological deviations during communication.