Introduction

Autistic spectrum disorders (ASDs) are characterized by impairments in social interaction and communication, and by restricted or repetitive behaviours and interests. The degree of impairment varies enormously. For example, individuals with low-functioning autism (LFA) may be mute or have atypical language, whilst individuals with high-functioning autism (HFA – used here to include individuals with Asperger syndrome) may have good language but nevertheless suffer from communication problems including impaired nonverbal communication. The underlying neural abnormalities associated with autism-related disorders are not well understood.

In addition to investigations of the defining behavioural impairments, as listed above, a number of studies have examined memory functions in people with ASDs. These have revealed an impairment in episodic memory (i.e. memory for events and episodes; Russell 1996; Bowler, Gardiner & Grice, 2000; Millward et al., 2000; Gardiner, Bowler & Grice, 2003), but not semantic memory (i.e. memory for facts or world knowledge – Tulving, 1972), at least in higher-functioning individuals (e.g. Ameli et al., 1988; Minshew et al., 1992; Bennetto, Pennington & Rogers, 1996; Siegel, Minshew & Goldstein, 1996; Farrant, Blades & Boucher, 1998).

Previous reports of individuals with developmental amnesia (DA) and a group of children born preterm (PT) have revealed a similar dissociation between episodic memory, which is selectively impaired, and factual memory, which is relatively preserved (e.g. Vargha-Khadem et al., 1997, 2003; Gadian et al., 2000; Isaacs et al., 2000, 2003).