Abstract
Fluent sentence production requires rapid syntax generation and word retrieval. We investigated how healthy aging affects these processes in two timed picture description tasks. In Experiment 1, young and older adults produced a syntactically related or unrelated prime prior to a target sentence (e.g., “the bell and the glove move up”). Both groups displayed significant facilitatory effects of priming on sentence onset latencies. In Experiment 2, participants produced sentences with initial coordinate or simple noun phrases (e.g., “the owl and the car move above the harp” / “the owl moves above the car and the harp”). On half the trials, the second picture (car) was previewed; critically, this previewed picture only fell within the initial phrase in the coordinate condition. Without preview, both age groups were slower to initiate sentences with larger coordinate phrases, suggesting a similar phrasal planning scope. However, age group differences did emerge in the preview conditions. Young adults displayed speed benefits of preview both within and outside the initial phrase. Whereas, older adults only displayed speed preview benefits within the initial phrase, and preview outside the initial phrase caused them to become significantly more error-prone. Thus, while syntactic planning scope appears unaffected by age, 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 generation.
Footnotes
This research was partly supported by an Economic and Social Research Council (ESRC) studentship awarded to Sophie M. Hardy from the University of Birmingham Doctoral Training Centre (grant number: ES/J50001X/1). The authors gratefully acknowledge the help of Denise Clissett, the coordinator of the Patient and Lifespan Cognition Database.
2 We note that some previous studies of incremental sentence production in aphasic patients have used non-young adults as controls; however, again the samples are often small and the age ranges are large (e.g., Lee, Yoshida, & Thompson, 2015; Martin et al., 2004; Scott & Wilshire, 2010; Speer & Wilshire, 2013). It is therefore difficult to draw any firm conclusions about the effect of old age on incremental planning from these studies.
