Abstract:

Older speakers frequently report more linguistic dysfluencies, verbose and even anomia in speech production than young speakers. The transmission deficit hypothesis assumes that normal aging reduces the activation transmission between the meaning and the word form of target words, which results in more failures. By contrast, the inhibition hypothesis assumes that the inhibitive ability about irrelevant information in older adults is decreased in comparison with young adults, thus more word retrieval failures in the old than in young adults. On the other hand, semantic interference effect and distractor word frequency effect have been observed in picture-word interference (PWI) task. Researchers interpreted the two effects via the competitive (i.e., lexical selection competition during lemma retrieval) and the non-competitive hypotheses (i.e., response exclusion hypothesis). The present study aims to investigate the influence of non-selective inhibition ability in picture naming by examining distractor frequency effect in young and older native Chinese speakers.

In the PWI task, participants were instructed to name pictures as quickly and accurately while ignoring distractor words. In experiment 1, we manipulated age (young vs. older), the frequency of distractor words (High vs. Low), and the onset interval between distractors and target pictures (-100 ms, 0 ms, and 100 ms). In experiment 2, we manipulated age, the frequency of distractor words, and the frequency of target names (High, Medium, and Low). The non-selective inhibition ability was measured by stop-signal task in both groups. Distractors and pictures were presented simultaneously.

Results indicated a target name frequency effect in both young and older groups. Importantly, we found distractor word frequency effects in young adults, but non in older adults. The distractor frequency effect in older adults was absent due to weaker phonological activation of distractor words, and thus support the transmission deficit hypothesis. The correlations between the ability of non-selection inhibition and distractor frequency effect were not significant in both groups, indicating this kind of ability did not affect the magnitude of distractor frequency effect. However, the ability of non-selection inhibition positively correlated with mean naming latencies only in older adults, indicating that the decrease of non-selective inhibition ability influences naming latencies in older adults, while the absence in the young due to the small variations of naming latencies, which need to be investigated further by covering a wide age range (18~80 years).

Key words: aging of speech production, picture-word interference task, distractor frequency effect, word frequency effect, non-selective inhibition