Working memory capacity and individual differences in the making of reinstatement and elaborative inferences

Inference comprehension from reading in individuals with mild cognitive impairment

Inference comprehension is a complex ability that recruits distinct cognitive domains, such as language, memory, attention, and executive functions. Therefore, it might be sensitive to identify early deficits in subjects with MCI. To compare the performance of subjects with mild cognitive impairment (MCI) in an inference reading comprehension task, and to analyze the correlations between inferential comprehension and other cognitive functions. We studied 100 individuals aged 60 and over, divided into MCI (50) [aMCI (35), naMCI (15)], and cognitively healthy individuals [controls (50)]. The Implicit Management Test (IMT) was used to assess inference in reading comprehension in five categories: explicit, logical, distractor, pragmatic, and "others". MCI group performed worse than controls in logical, pragmatic, distractor, and "others" questions (p < 0.01). The aMCI and naMCI subgroups presented a similar performance in all types of questions (p > 0.05). We observed significant correlations between the total IMT score and the TMT-A in the naMCI group (r = - 0.562, p = 0.036), and the Rey-Osterrieth Complex Figure and RAVLT tasks in the aMCI group (r = 0.474, p = 0.010 and r = 0.593, p = 0.0001, respectively). The MCI group as a whole performed worse than controls on the logical, pragmatic, other and distractor questions, and consequently on the total score. There were no differences in explicit questions, which impose lower inferential demands. The aMCI group suffered a significant impact from memory on inference comprehension, and difficulties in executive functions impacted naMCI performance. The IMT was useful to differentiate MCI patients from cognitively healthy individuals, but not MCI subgroups among themselves.

Inference comprehension in text reading: Performance of individuals with right- versus left-hemisphere lesions and the influence of cognitive functions

Background

Right-hemisphere lesions (RHL) may impair inference comprehension. However, comparative studies between left-hemisphere lesions (LHL) and RHL are rare, especially regarding reading comprehension. Moreover, further knowledge of the influence of cognition on inferential processing in this task is needed.

Objectives

To compare the performance of patients with RHL and LHL on an inference reading comprehension task. We also aimed to analyze the effects of lesion site and to verify correlations between cognitive functions and performance on the task.

Methods

Seventy-five subjects were equally divided into the groups RHL, LHL, and control group (CG). The Implicit Management Test was used to evaluate inference comprehension. In this test, subjects read short written passages and subsequently answer five types of questions (explicit, logical, distractor, pragmatic, and other), which require different types of inferential reasoning. The cognitive functional domains of attention, memory, executive functions, language, and visuospatial abilities were assessed using the Cognitive Linguistic Quick Test (CLQT).

Results

The LHL and RHL groups presented difficulties in inferential comprehension in comparison with the CG. However, the RHL group presented lower scores than the LHL group on logical, pragmatic and other questions. A covariance analysis did not show any effect of lesion site within the hemispheres. Overall, all cognitive domains were correlated with all the types of questions from the inference test (especially logical, pragmatic, and other). Attention and visuospatial abilities affected the scores of both the RHL and LHL groups, and only memory influenced the performance of the RHL group.

Conclusions

Lesions in either hemisphere may cause difficulties in making inferences during reading. However, processing more complex inferences was more difficult for patients with RHL than for those with LHL, which suggests that the right hemisphere plays an important role in tasks with higher comprehension demands. Cognition influences inferential processing during reading in brain-injured subjects.

The role of working memory in inferential sentence comprehension

Existing literature on inference making is large and varied. Trabasso and Magliano (Discourse Process 21(3):255-287, 1996) proposed the existence of three types of inferences: explicative, associative and predictive. In addition, the authors suggested that these inferences were related to working memory (WM). In the present experiment, we investigated whether WM capacity plays a role in our ability to answer comprehension sentences that require text information based on these types of inferences. Participants with high and low WM span read two narratives with four paragraphs each. After each paragraph was read, they were presented with four true/false comprehension sentences. One required verbatim information and the other three implied explicative, associative and predictive inferential information. Results demonstrated that only the explicative and predictive comprehension sentences required WM: participants with high verbal WM were more accurate in giving explanations and also faster at making predictions relative to participants with low verbal WM span; in contrast, no WM differences were found in the associative comprehension sentences. These results are interpreted in terms of the causal nature underlying these types of inferences.