Abstract
Prior studies on language processing in aging have shown that older adults experience integration difficulties for contextually unpredictable target words (as indicated by low cloze probabilities in prior ratings), and that such comprehension difficulties are more likely to occur under more demanding processing conditions (e.g., dual-task situations). However, these effects have primarily been demonstrated for conditions when cloze probability of the linguistic stimuli was very low. The question we asked here was do dual-task demands also impair comprehension when target words provide a good, but not perfect, match with prior context? We used a dual-task design, consisting of a sentence comprehension and secondary motor tracking task. Critical target words were those which were not perfectly predictable based on context (words with a cloze probability of 0.7), as opposed to words that were near perfectly predictable based on context (cloze probabilities of 0.99). As a measure to index online processing difficulty for less expected target words, we took into account participants’ pupil size. Separate mixed effects models were fit for language comprehension, motor tracking, and pupil size, showing the following: (1) dual-task demands led to age-related comprehension difficulties when target words were less expected (as opposed to very highly expected), (2) integration difficulty in older adults was related to cognitive overload as less expected sentence continuations progressed over time, resulting in behavioral trade-offs between language comprehension and motor tracking, and (3) lower levels of working memory were predictive of whether or not older adults experienced cognitive overload when processing less expected words. In sum, more demanding processing conditions lead to comprehension impairments when words are highly unpredictable based on context, as many prior studies showed. Comprehension impairments among older individuals also occur for conditions when words provide a good, but not perfect, match with prior context. Higher working memory capacity can alleviate such impairments in older adults, thereby suggesting that only high-WM older adults have sufficient cognitive resources to pre-activate words that complete a sentence context plausibly, but not perfectly.
Highlights
Previous studies have demonstrated that aging impairs comprehension of words or sentence fragments that are unexpected based on semantic constraints of prior context (Federmeier et al, 2002, 2010; Federmeier and Kutas, 2005; Wlotko et al, 2012)
Age-related comprehension impairments for unexpected words have primarily been demonstrated for targets that were very low in cloze probability, in other words, for sentence continuations that were highly unpredictable based on context
Our data here indicate that general working memory capacity among older listeners, but not processing speed or context updating, was related to the gradual decline in pupil size that we found in older adults when they were listening to less expected sentence continuations
Summary
Previous studies have demonstrated that aging impairs comprehension of words or sentence fragments that are unexpected based on semantic constraints of prior context (Federmeier et al, 2002, 2010; Federmeier and Kutas, 2005; Wlotko et al, 2012). Such age-related comprehension impairments are more likely to occur under more demanding processing conditions, such as in a dual-task situation when the execution of a secondary task taxes cognitive resources (Tun et al, 2002, 2009; Häuser et al, 2018). Age-related comprehension impairments for unexpected words have primarily been demonstrated for targets that were very low in cloze probability, in other words, for sentence continuations that were highly unpredictable based on context. Our main question was whether older adults experience comprehension difficulties for those target words that do not perfectly match with semantic context
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