Abstract
Healthy aging does not affect all features of language processing equally. In this study, we investigated the effects of aging on different processes involved in fluent sentence production, a complex task that requires the successful execution and coordination of multiple processes. In Experiment 1, we investigated age-related effects on the speed of syntax selection using a syntactic priming paradigm. Both young and older adults produced target sentences quicker following syntactically related primes compared to unrelated primes, indicating that syntactic facilitation effects are preserved with age. In Experiment 2, we investigated age-related effects in syntactic planning and lexical retrieval using a planning scope paradigm: participants described moving picture displays designed to elicit sentences with either initial coordinate or simple noun phrases and, on half of the trials, the second picture was previewed. Without preview, both age groups were slower to initiate sentences with larger coordinate phrases, suggesting a similar phrasal planning scope. However, age-related differences did emerge relating to the preview manipulation: while young adults displayed speed benefits of preview in both phrase conditions, older adults only displayed speed preview benefits within the initial phrase (coordinate condition). Moreover, preview outside the initial phrase (simple condition) caused older adults to become significantly more error-prone. Thus, while syntactic planning scope appears unaffected by aging, older adults do appear to encounter problems with managing the activation and integration of lexical items into syntactic structures. Taken together, our findings indicate that healthy aging disrupts the lexical, but not the syntactic, processes involved in sentence production.
Highlights
Further post hoc pairwise comparisons revealed that for young adults, there was a significant benefit of preview in both the coordinate [81 ms (8.9%), χ2(1) = 18.20, p < 0.001] and simple [45 ms (5.3%), χ2(1) = 9.03, p = 0.002] phrase conditions, the magnitude of the effect was distinctly larger when the preview fell within the initial phrase
Further insight into possible age-related effects may be gleamed from separate age group analyses (Tables 5B,C). This revealed that the interaction between preview and initial phrase type remained significant for older adults (p = 0.016), but not for young adults (p = 0.352)
Summary The main findings of Experiment 2 can be summarized as follows: (1) as in Experiment 1, older adults were slower and more errorprone than young adults; (2) our task elicited a reliable phrasal planning scope effect that was unaffected by healthy aging; and (3) while young adults’ displayed speed benefit of preview in both phrase conditions, older adults only benefited when the preview fell within the initial phrase and produced significantly more errors when the previewed lexical item fell within the second phrase
Summary
Summary The main findings of Experiment 2 can be summarized as follows: (1) as in Experiment 1, older adults were slower and more errorprone than young adults; (2) our task elicited a reliable phrasal planning scope effect that was unaffected by healthy aging; and (3) while young adults’ displayed speed benefit of preview in both phrase conditions, older adults only benefited when the preview fell within the initial phrase and produced significantly more errors when the previewed lexical item fell within the second phrase Together, this suggests that there were age group differences in lexical processing during sentence planning which only emerged when the preview fell outside of the initial phrase. Fiedler et al (2012) argue that it is important to rigorously explore all possible findings within a dataset, even when they are accompanied by some apparently null results, in order to prevent against the risk of a false negative (the discovery of a false null result) (see Wei et al, 2012)
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