Executive function and theory of mind performance of boys with fragile‐X syndrome

Abstract

Fragile-X syndrome is the most common genetically inherited cause of intellectual disability. People with this syndrome typically show a behavioural profile of abnormal social interactions which are similar in some ways to those seen in people with autism. The present study investigated whether cognitive processes which have been hypothesized to underlie social abnormalities associated with autism are also impaired in boys with fragile-X syndrome without autistic spectrum disorders. Eight boys with fragile-X syndrome and eight with intellectual disability of unknown aetiology, matched on receptive verbal ability, age and with no diagnosis of autism, were tested on a battery of theory of mind and executive function tasks. Significantly more boys with fragile-X syndrome failed the simplest theory of mind task. However, this could be attributed to overall level of ability rather than group membership. No differences were found between the groups on any other measures used. A proportion of both groups failed first- and second-order false belief tasks. The performance of both groups on the executive function measure was at the floor of the test. At low levels of overall ability, the performance of boys with fragile-X syndrome and boys with intellectual disability of unknown aetiology may be more similar than they are different The implication of this result for clinical interventions is discussed.

Is Theory of Mind Understanding Impaired in Males with Fragile X Syndrome?

“…In accordance with the findings of Garner et al (1999) and Cornish et al (2005) that males with FXS (without autism) performed similarly to other children with intellectual disability on tests of theory of mind, it was predicted that boys with FXS (without autism) will not have a specific theory of mind deficit. It was predicted that their performance would be related to the executive demands (i.e., working memory and inhibitory control) of the task.…”

“…However, the perspectivetaking task used in this study was originally designed for children so may have lacked the sensitivity to detect subtle deficits in theory of mind in adult participants. Garner, Callias and Turk (1999) addressed theory of mind in boys with FXS and reported that significantly more children with FXS failed standard false belief tasks than a comparison group of children with intellectual disability of unknown aetiology.…”

“…Although the standard false belief tasks used by Garner et al (1999) and Cornish et al (2005) included check questions to ensure that the participant could remember crucial facts about the story, remembering these facts is not the only demand that the false belief task makes on working memory. Since children with FXS have well-attested impairments in working memory that are disproportionate to their general level of intellectual impairment (Cornish, Munir & Cross, 2001), it could be that any difficulty they have on false belief tasks arises from working memory impairment, rather than a more specific "theory of mind" impairment.…”

Language development and fragile X syndrome: Profiles, syndrome‐specificity, and within‐syndrome differences

“…Cognitive skills that are especially delayed or impaired include those involved in auditory short-term memory [Freund and Reiss, 1991], the processing of sequential information Burack et al, 1999], and the directing and sustaining of attention Bregman et al, 1988;Mazzocco et al, 1993]. In contrast, some cognitive skills are relatively strong in FXS, including those involved in processing simultaneous information [Dykens et al, 1989], entering and retrieving information from long-term memory [Freund and Reiss, 1991], and distinguishing between the self 's and other people's representations of the world [Garner et al, 1999]. This profile of (relative) cognitive strengths and weaknesses differs from the profiles of other neurodevelopmental disorders, such as Down syndrome [Dykens et al, 2000], which suggests that the profile and causes of linguistic impairments in FXS will be different compared to other disorders [Abbeduto and McDuffie, 2007].…”

Fragile X syndrome

“…Self-injury is usually highly specific, taking the form of biting over the base of the thumb in response to anxiety, excitement and other states of psychological arousal [61]. Imitative and symbolic play is usually delayed but does develop [62] and the presence and level of theory of mind and executive functioning are usually as expected for general developmental ability levels [63]. Stereotyped and repetitive behaviours are very common, in particular hand flapping [64] and insistence on routine and environmental sameness.…”