Understanding Theory of Mind–pragmatics relationship through the spectrum of neurodegenerative diseases

Abstract

Our understanding of how pragmatic skills change in ageing is not systematic. Even less is known about the effects of pathological ageing—particularly in the context of neurodegenerative diseases—on pragmatic competence, changes in Theory of Mind and the potential inter-relationship between these domains. Given that pragmatic competence relies on a wide range of cognitive functions, examining pragmatic changes in speakers with neurodegenerative diseases may clarify whether these alterations are inherently pragmatic or arise from deficits in other cognitive domains, such as impairments in Theory of Mind. In this work, I inquire into how eight neurodegenerative conditions (behavioural variant frontotemporal dementia, semantic dementia, Alzheimer’s disease, amnesic mild cognitive impairment, Parkinson’s disease, Lewy body dementia, cerebellar neurodegenerative disorders and right temporal degeneration) compromise pragmatic abilities and explore whether such impairments are linked to changes in Theory of Mind. Based on a narrative review of available experimental evidence, I come to several conclusions. First, only one neurodegenerative disease (behavioural variant frontotemporal dementia) shows up with pragmatic deficits directly linked to impairment in Theory of Mind. In the rest of the conditions, pragmatic deficits, although linked to Theory of Mind, derive from impairments in other cognitive functions (such as working memory or executive functions). Overall, pragmatic abilities are better predicted by their internal gradation (which abilities impose more cognitive load) than by the neural pathways of the diseases.