Executive function and theory of mind performance of boys with fragile-X syndrome.
Low-ability boys with fragile-X show the same theory-of-mind and executive-function profile as other low-ability boys once IQ is equalized.
01Research in Context
What this study did
Hatton et al. (1999) compared boys with fragile-X syndrome to boys with other intellectual disabilities.
They gave both groups the same theory-of-mind and executive-function tasks.
Then they asked: do the fragile-X boys still look different once overall IQ is held constant?
What they found
After IQ was controlled, the two groups scored the same.
Most boys in both groups hit the floor on executive tasks.
The label fragile-X added no extra information about social-cognitive skill.
How this fits with other research
Dickson et al. (2005) later saw fragile-X boys make unique error types on theory-of-mind tests compared to Down-syndrome peers.
The studies seem to clash, but K used a different control group and kept IQ constant only across broad ranges.
Dougherty et al. (1994) had already shown the same null pattern in women: once IQ is partialed out, carrier status does not predict social-cognition scores.
Howard et al. (2023) extend the picture to school-aged girls, finding specific math and attention weaknesses in FXS even when verbal IQ is matched.
Why it matters
For low-ability learners, skip the syndrome checklist and test the child in front of you.
Write goals at their developmental level, not their diagnostic label.
If you need a baseline, probe working memory or planning; these may separate FXS from other IDs better than social-cognition tasks.
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02At a glance
03Original 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.
Journal of intellectual disability research : JIDR, 1999 · doi:10.1046/j.1365-2788.1999.00207.x