A 20-Year Systematic Review of the 'Reading the Mind in the Eyes' Test across Neurodegenerative Conditions

Abstract

Social cognition has a broad theoretical definition, which includes the ability to mentalise, i.e., recognise and infer mental states to explain and predict another's behaviour. There is growing recognition of the clinical, diagnostic, and prognostic value of assessing a person's ability to perform social cognitive tasks, particularly aspects of theory of mind, such as mentalising. One such measure of mentalising is the 'Reading the Mind in the Eyes' test (RMET). This systematic review and meta-analysis consider performance on the RMET, applied to people with neurodegenerative conditions in matched control studies, since its publication in 2001. Overall, this review includes 22 papers with data from N = 800 participants with neurodegenerative conditions: Alzheimer's disease, n = 31; Parkinson's disease, n = 221; Lewy body dementia, n = 33; motor neuron disease, n = 218; Huntington's disease n = 80; multiple sclerosis, n = 217; and N = 601 matched typical controls. Our meta-analyses show that deficits in mentalising, as measured by the RMET, are consistently reported across neurodegenerative conditions, with participants in both early and late disease stages being affected. Social cognition is an emerging field of cognitive neuroscience requiring specific and sensitive measurement across each subdomain. Adult-based meta-normative data feature, for which future groups or individuals could be compared against, and hypotheses relating to the source of these mentalising deficits are further discussed. This review was registered with PROSPERO (CRD42020182874).

Keywords: Alzheimer’s disease; Huntington’s disease; Lewy body dementia; Parkinson’s disease; motor neuron disease; multiple sclerosis; neurodegenerative diseases; social cognition; the ‘Reading the Mind in the Eyes’ test.

Figure 1

PRISMA flow diagram of studies included in this systematic review.

Figure 2

Forest plot of effect sizes with their 95% confidence intervals (CIs), and respective weights are shown for each individual study on RMET when compared with typical controls (TCs). The average effects of all studies combined is represented by the black diamond at the bottom of the graph. Due to high heterogeneity within this comparison, effect sizes are represented here as a standardised mean difference (SMD) [14,15,16,35,36,37,38,39,40,41,42,43,44,45,46,47,48].

Figure 3

Forest plot of effect sizes, their 95% confidence intervals, and the respective weight of each neurodegenerative category (ND) on RMET performance as compared with typical controls (TCs). The average effects of all studies combined is represented by the black diamond at the bottom of the graph. Due to high heterogeneity within this comparison, effect sizes are represented here as a standardised mean difference (SMD). See Supplementary Material one for overview of neurodegenerative disease characteristics: Alzheimer’s Disease (AD); Dementia with Lewy Body (DLB); Huntington’s Disease (HD); Motor Neurone Disease (MND); Multiple Sclerosis (MS); Parkinson’s Disease (PD).