Healthy Ageing and Sentence Production: Disrupted Lexical Access in the Context of Intact Syntactic Planning

Abstract

Sentence production requires rapid syntax generation and word retrieval. We investigated how healthy ageing affects these processes. In Experiment 1, syntactic priming significantly facilitated sentence production speed for both young and older adults. In Experiment 2, participants produced sentences with initial coordinate or simple 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. Without preview, both age groups were slower to initiate sentences with larger coordinate phrases, suggesting a similar planning scope. Young adults displayed speed benefits of preview both within and outside the initial phrase; however, older adults only displayed speed preview benefits within the initial phrase, and preview outside the initial phrase significantly increased error rates. Thus, syntactic planning scope appears unaffected by age, but there is age-related decline in the integration of lexical items into syntactic structures.

Structural priming is determined by global syntax rather than internal phrasal structure: Evidence from young and older adults.

“…age-related differences exist in on-line sentence planning (i.e., older adults' increased sensitivity to phrasal properties and boundaries; Hardy et al, 2018).…”

“…To our knowledge, only one study to date has specifically examined on-line sentence planning processes in older adults. Hardy et al (2018) found that, although both young and older adults took longer to initiate sentences with a larger initial phrase, there were age group differences in the flexibility of planning scope.…”

“…Indeed, evidence suggests that speakers typically plan the first phrase before speech onset with planning for the rest of the sentence occurring during articulation (see Wheeldon, 2013, for a review). For example, speakers have been found to take longer to initiate sentences containing larger initial phrases, supporting a phrasal scope of advanced planning (Hardy, Segaert, & Wheeldon, 2018; Levelt & Maasen, 1981; Martin, Crowther, Knight, Tamborello, & Yang, 2010; Martin, Yan, & Schnur, 2014; Smith & Wheeldon, 1999), although the degree and type of preplanning may vary according to the linguistic structure of a given language (Hwang & Kaiser, 2014, 2015; Myachykov, Scheepers, Garrod, Thompson, & Fedorova, 2013). Taken together, this highlights why it is important to examine choice and onset latency priming effects in conjunction, to gain a more complete understanding of the processes involved in fluent sentence production.…”

“…One explanation for this age-related effect on lexical processing may be that older adults' planning scope is more rigidly fixed to phrasal boundaries. Hardy et al (2018)'s study therefore provides the first evidence that healthy ageing affects some aspects of on-line sentence planning; however, many questions are still to be addressed. Within our study, we aimed to specifically investigate older adults' sentence planning in a task in which syntactic choice was also involved and in which repetition of the global and internal structure was manipulated between the prime and the target.…”

“…As such, our study will provide added insight into age-related effects on online sentence planning. It could be that older adults’ increased sensitivity to phrasal boundaries (as found by Hardy et al, 2018) means that they are also more sensitive to the constituent features within phrases. This may in turn mean that, compared with young adults, the magnitude of the latency priming effects displayed by older adults may be more strongly influenced by whether or not the internal noun phrase structure is repeated between the prime and target.…”