Journal of the International Neuropsychological Society (2010), 16, 287–296. Copyright © INS. Published by Cambridge University Press, 2010. doi:10.1017/S1355617709991329 287 INTRODUCTION In the past 25 years, research on the neuropsychological as- pects of multiple sclerosis (MS) has burgeoned. Even though cognitive dysfunction in MS is not rare, some neurologists specializing in MS still tend to underestimate the prevalence of MS-related cognitive impairments (Fischer, Foley, Aikens, Ericson, Rao, & Shindell, 1994). In fact, cognitive dysfunc- tion occurs in 40–70% of cases, depending on the sample (Achiron & Barak, 2006; Amato, Zipoli, & Portaccio, 2006; Huijbregts, Kalkers, de Sonneville, de Groot, & Polman, 2006; Potagas et al., 2008; Rao et al., 1991a). Assessment of social cognition in patients with multiple sclerosis JULIE OUELLET, 1 PETER B. SCHERZER, 2,3 ISABELLE ROULEAU, 2,3,4 PHILIPPE MÉTRAS, 3 CAROLINE BERTRAND-GAUVIN, 2,3 NADÉRA DJERROUD, 2,3 ÉMILIE BOISSEAU, 2 and PIERRE DUQUETTE 4 1 Institut de Réadaptation Gingras-Lindsay de Montréal, Montréal, Canada 2 Institut des Sciences Cognitives, Université du Québec à Montréal, Montréal, Canada 3 Département de psychologie, Université du Québec à Montréal, Canada 4 Hôpital Notre-Dame du CHUM, Montréal, Canada (Received April 15, 2009; Final Revision December 23, 2009; Accepted December 23, 2009) Abstract We examined the capacity of patients with multiple sclerosis (MS) to attribute mental states to others and to identify cognitive abilities that subserve theory of mind (ToM). In this article, we report findings on 41 out-patients with diagnosed MS who underwent detailed neuropsychological and social-cognitive assessment. They were subdivided into a cognitively intact (n=15) and cognitively impaired (n=26) group according to their neuropsychological test results. Their results were compared with those of 20 age- and education-matched controls. MS patients with cognitive impairments were found to have more difficulties attributing mental states to others than did cognitively intact MS patients and normal controls on two ToM measures; short stories (Happé, Winner, & Brownell, 1998) and video clips (Ouellet, Bédirian, Charbonneau, & Scherzer, 2009). When attention, memory, and working memory were controlled, performance on the WAIS-III Picture Arrangement task accounted for 17.3% of the variance in perfor- mance on the video clips task. Performance on a WAIS-III index composed of Similarities and Comprehension subtests, accounted for 7.0% of the variance in performance on the short stories task. These results provide some preliminary information on the effect of MS-related cognitive deficits on the ability to attribute mental states to others. ( JINS, 2010, 16, 287–296.) Key words: Multiple sclerosis, Cognitive dysfunction, Theory of mind, Short stories, Naturalistic task, Literal interpretation Correspondence and reprint requests to: Peter Scherzer, PhD, Départe- ment de psychologie, Université du Québec à Montréal, Case postale 8888, Succursale Centre-ville, Montréal, (Québec), Canada H3C 3P8. E-mail: scherzer.peter_b@uqam.ca The types of cognitive deficits seen in MS have been well characterized. Controlled neuropsychological studies have consistently shown decline on tasks assessing recent memory, attention, processing speed, working memory, visuo-spatial abilities, and executive functions (Bobholz & Rao, 2003; Brassington & Marsh, 1998; Fischer et al., 1994; Pelosi, Geesken, Holly, Hayward, & Blumhardt, 1997; Rao, 1996; Rao, Grafman, DiGiulio, Mittenberg, & Bernardin, 1993; Rao et al., 1991a). Information processing speed may be most affected by the impact of MS on cognitive functioning over time (Denney, Lynch & Parmenter, 2008). Although specific neurological deficits and fatigue are frequently the most conspicuous sources of functional impairment in patients with MS, in many of them, cognitive dysfunction may be the most disabling manifestation of the disease. It may have a severe negative impact on everyday function and quality of life (Amato, Ponziani, Siracusa, & Sorbi, 2001; Benito-Leon, Morales, & Rivera-Navarro,