Abstract:

As the development and acceleration of world population aging process, people pay more attention to the aging of cognitive function. As one of the basic cognitive function, speech processing has been widely discussed and evidence showed that the ability of speech comprehension preserved well throughout life while the ability of speech production decline. Why do these happen? In some research, aging people showed disadvantages on fulfilling tasks that involved competitions. It seems that changing of inhibiting capacity can be the plausible and essential reason. However, we don’t believe it should be the only reason. Three experiments investigated the inhibition deficit hypothesis in the aging of speech production across different tasks. In Experiment 1, Stroop effect was tested between the elderly and the young. Results showed that the elderly have greater difficulty in producing the right words than young when semantic information of the given words was not consistent with its printed color (i.e., word “RED” was written in red). Elderly seems to have greater disadvantages than young in inhibiting automatic activation of semantics. In Experiment 2, manipulating the context to the given targets, potential competitors were activated at different levels: high or low. Results turned out that the ability to inhibit the potential word of the elderly was equivalent to the young at the low activation level (experiment 2a), while the elderly appeared to have inferior inhibition ability at the high activation level (experiment 2b). We believed that the inhibitory deficit does not always happen to elderly.Activation levels of potential competitors plays important role in speech. For more evidence, we used sentence production task in Experiment 3, and investigated the above assumption in sentence level. The results showed that there were greater difficulties in inhibiting the confliction between pictures’ roles for the elderly, and the performance of sentence production was significantly worse with the elderly than the young when strongly conflictions were involved. In conclusion, the three experiments in the present research showed that: (1) The overall response of the elderly was worse than the young in theses speech production tasks; (2) Inhibitory deficit plays important role in speech of the elderly, but activation level of the potential competitors, which will get inhibition involved, should not be ignored when aging of speech was discussed.

Key words: inhibition, aging of speech production, working memory, activation level