Exploring memory updating ability in individuals with low and high levels of autistic-like traits

Autism Spectrum Disorder (ASD) is a pervasive developmental disorder characterised by impairments in social interaction and communication, and repetitive and stereotypic patterns of thoughts and behaviours. In addition, the symptoms associated with ASD are believed to occur along a continuum of severity, extending to typically-developing people with and without a family history of the disorder. These lesser symptoms have become more commonly known to encompass a broader autism phenotype. The widespread nature of the associated difficulties highlights the importance of investigating the underlying basis of the disorder.

One class of theory that has emerged from investigations of the cognitive underpinnings of ASD proposes that the difficulties associated with the disorder arise from impairments in executive functions. Executive functions encompass a wide range of higher-level cognitive abilities that enable an individual to flexibly change his/her thoughts and behaviours in accordance with environmental changes, in order to maintain appropriate goal-directed behaviour. However, studies in the realm of executive dysfunction theory have largely focused on a particular subset of executive functions, viz. inhibition, planning, and set-shifting (or cognitive flexibility). One additional executive function that has received much less attention within the ASD literature is memory updating.

Memory updating has been conceptualised as related to but separate from cognitive flexibility, and is implicated in various everyday activities such as keeping track of unfolding news events. For example, when reading a news report, the reader constructs a situation model based on the information presented in the report; if the report contains a retraction or correction of initially plausible but ultimately incorrect information, the reader must update the situation model in order to keep an up-to-date version of the report in memory.

Previous studies have found impaired set-shifting ability in individuals with ASD, who have been observed to exhibit greater difficulties on various tasks requiring this ability compared to typically-developing counterparts (e.g., greater difficulty shifting to a new sorting rule in the Wisconsin Card Sorting Test). Given their impaired set-shifting ability, it is possible that individuals with ASD may also have limited memory updating ability. However, no studies have considered this.

The current thesis presents an exploration of memory updating in individuals with low and high levels of autistic-like traits. To this end, the Autism-Spectrum Quotient (AQ; Baron-Cohen, Wheelwright, Skinner, Martin, & Clubley, 2001) was used to select university students forming low- and high-AQ groups for each experiment. The AQ is commonly used to assess levels of autistic-like traits in the general population, and numerous studies have found that individuals with high levels of autistic-like traits exhibit similar cognitive profiles to individuals with ASD (e.g., Almeida, Dickinson, Maybery, Badcock, & Badcock, 2013; Grinter, Maybery, et al., 2009).

In the following chapters, I first present background literature on three main cognitive theories commonly used to explain the symptoms associated with ASD, followed by five experiments employing different methodologies to investigate memory updating ability in individuals with low and high levels of autistic-like traits. Experiments 1 to 3 employed complex narrative reports involving retracted information to emulate updating of situation models of an unfolding event. Experiments 4 and 5 employed the homograph-reading task (Frith & Snowling, 1983) and a basic memory updating task, respectively, to further delve into memory updating ability in individuals with low and high levels of autistic-like traits.

Overall, results do not provide conclusive evidence that individuals with high levels of autistic-like traits have limited memory updating ability compared to individuals with low levels of autistic-like traits. However, it is important for future research to investigate memory updating ability further in a more general population with high levels of autistic-like traits, as the current research program relied on samples of high-functioning university students. Investigating memory updating ability in individuals with an ASD diagnosis would also be valuable in establishing whether there is continuity or discontinuity along the autism spectrum in regard to memory updating ability.