Häuser Katja I, Demberg Vera, Kray Jutta
Department of Psychology, Saarland University, Saarbrücken, Germany.
Collaborative Research Center on Information Density and Linguistic Encoding, Saarland University, Saarbrücken, Germany.
Front Psychol. 2019 Mar 29;10:709. doi: 10.3389/fpsyg.2019.00709. eCollection 2019.
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.
先前关于衰老过程中语言处理的研究表明，老年人在处理上下文不可预测的目标词时会遇到整合困难（如先前评级中的低完形概率所示），并且这种理解困难在要求更高的处理条件下（如双重任务情境）更有可能发生。然而，这些影响主要是在语言刺激的完形概率非常低的条件下得到证明的。我们在此提出的问题是，当目标词与先前语境有较好但并非完美的匹配时，双重任务要求是否也会损害理解？我们采用了一种双重任务设计，包括句子理解和次要运动跟踪任务。关键目标词是那些基于上下文不能完全预测的词（完形概率为0.7的词），而不是基于上下文几乎可以完全预测的词（完形概率为0.99的词）。作为衡量较难预期目标词在线处理难度的指标，我们考虑了参与者的瞳孔大小。分别对语言理解、运动跟踪和瞳孔大小拟合了混合效应模型，结果如下：（1）当目标词较难预期时（与非常容易预期的词相反），双重任务要求会导致与年龄相关的理解困难；（2）随着较难预期的句子延续时间的推移，老年人的整合困难与认知过载有关，导致语言理解和运动跟踪之间的行为权衡；（3）较低水平的工作记忆可预测老年人在处理较难预期的词时是否会经历认知过载。总之，正如许多先前研究表明的那样，当基于上下文单词高度不可预测时，要求更高的处理条件会导致理解受损。在单词与先前语境有较好但并非完美匹配的情况下，老年人也会出现理解受损。较高的工作记忆容量可以减轻老年人的这种损伤，从而表明只有高工作记忆容量的老年人有足够的认知资源来预先激活合理但不完美地完成句子语境的单词。
