Signaling of Non-Comprehension by Boys with Idiopathic Autism, Fragile X Syndrome and Autism, and Typical Development

Background:  An important component of discourse is to signal to a speaker when you do not comprehend their message.  Abbeduto and colleagues (1997, 2008) found that children with intellectual disability (resulting from Down syndrome or fragile X syndrome) make fewer signals of non-comprehension than mental age matched typically-developing peers when presented with inadequate information from the examiner.  What is unknown is whether children with autism, known to have deficits in pragmatic language (Tager-Flusberg, 1999), show similar non-comprehension signaling as children with fragile X syndrome or if non-comprehension deficits are largely driven by intellectual disability. 

Objectives: We sought to determine if and how children with idiopathic autism signal non-comprehension and whether their signaling techniques differ from children with fragile X syndrome with autism and from typically-developing peers.   

Methods: We assessed signals of non-comprehension in boys with idiopathic autism (n = 25), fragile X syndrome with autism (n = 46), and typical development (n = 39), ages 3-17. Following procedures of Abbeduto and colleagues (2008), children were asked to complete a picture matching task by following the directions of an examiner, which contained the appropriate level of detail or incomplete details, including new vocabulary, erroneous information, and not enough information. The proportion of signals of non-comprehension out of possible items was calculated for each condition.  All children also completed an appropriate module of the Autism Diagnostic Observational Scale (ADOS) and assessments of theory of mind.

Results:  When covarying for receptive language and non-verbal mental ages, we replicated previous results that boys with fragile X syndrome with autism had fewer signals of non-comprehension than their typically-developing peers across conditions with incomplete information (t₈₃ = 4.467, p < 0.001).  The boys with idiopathic autism did not differ from their typically-developing peers and made significantly more signals of non-comprehension than the boys in the fragile X group (t₆₉ = 4.105, p < 0.001).  ADOS severity scores and theory of mind performance were correlated with proportion of non-comprehension signaling (r = -0.286, p < 0.01; r = 0.286, p < 0.01, respectively), with greater severity and weaker theory of mind linked to less frequent signaling of non-comprehension, but these correlations were driven by group differences on the measures.

Conclusions: The present results suggest that the pragmatic language deficits associated with autism do not convey additional impairments in non-comprehension signaling as children with idiopathic autism did not differ from typically-developing peers.  While autism severity and theory of mind did predict non-comprehension signaling, the relationships were driven by group differences on the measures and were not present within groups.  This suggests that previous reports of impairments in non-comprehension signaling by children with fragile X syndrome are not due to overlap in pragmatic deficits with autism, but to another component of the disorder.

References

Abbeduto L, Murphy MM, Kover ST, Giles ND, Karadottir S, et al. (2008). Am J Ment Retard, 113(3): 214-230.

Abbeduto L, Short-Meyerson K, Benson G, & Dolish J (1997). JSLHR, 40:20-32.

Tager-Flusberg H (1999). Int Rev Psychiatry, 11(4): 325-334.