The researchers investigated the meta-representational abilities of four high-functioning autistic adults (aged 19-29 years) on the basis of their use of linguistic expression forms of epistemic modality. The study is based on data drawn from natural conversations in Dutch. Parallel to an existing in-depth corpus study of epistemic modal expression forms in normal language use (the control data for the present study), the occurrences in the data of four types of such expression forms -- modal adverbs, predicative adjectives, mental state predicates, and auxiliaries -- are analyzed in terms of their quantitative and qualitative comparability to the normal data.

The results show normal usage of these forms for three of the subjects. Only one subject, with the lowest general IQ of the four, showed problems with particular types of usages. It is argued that these results show that although there is some truth to the classical "Theory of Mind" theories of autism, they turn out to be too simple to account for the data. Suggestions for an alternative way of thinking about the nature of autism are offered.