Item-Memory for Words, Pictures, Abstract Shapes and Nonsense-Words in Adults with Autism Spectrum Disorder

Background:  Memory in ASD is characterised by a specific pattern of strength and difficulties (Boucher & Bowler, 2008) that include impairments in episodic memory whilst semantic memory is relatively preserved (Tulving, 2002). Memory in ASD is usually tested by asking individuals to memorise a list of words or a set of pictures of daily objects. Since ASD is associated with varying degrees of language and social-communication impairments (APA, 2013; Bennett et al., 2008), it is possible that memory difficulties in relation to such materials reflect language difficulties to some extent. This could be related to difficulties of ASD individuals to use categorical information to support their memory (Gaigg et al., 2008). Therefore it is unclear if findings generalise to non-verbal materials.

Objectives:  The aim was to replicate prior findings of difficulties with episodic but not semantic memory in ASD with a larger sample. We were also interested to see if findings for words and pictures can be generalised to non-meaningful pictorial and verbal materials. Finally, it was of interest to examine which materials would be remembered best by both groups.

Methods:  Sixty-four (32 TD, 32 ASD) adults (age-range: 22-65 years) matched on intelligence, age and gender were asked to study a sequence of blocks of words, pictures, nonsense-words and abstract shapes with 10 items each. Their memory was tested after all blocks using a ‘yes-no’ followed by the ‘Remember-Know’ (RK) recognition memory procedure (Tulving, 2002). Participants were also asked to justify any R responses by describing what they remembered. After the task they were given a questionnaire enquiring about the strategy they used for remembering the materials (e.g. I looked at the item, I imagined the word as a picture in my head, I told myself a story about the item). In three follow-up tasks participants were asked to assign names to the pictures or form associations for nonsense-words and shapes to measure participants’ ability of establishing meaning for the materials.

Results:  Preliminary data (25 TD, 19 ASD) suggest that pictures were remembered better than all other materials by both groups. Both groups showed significantly higher R compared to K responses. In addition the TD group presented significantly higher R responses compared to the ASD group. The TD groups’ recognition performance was overall better than the ASD groups’ recognition. There was no difference in the quality of R responses between groups. Recognition differences between groups seem to be related to differences in strategy use and differences in establishing meaning for the materials to support memory. The TD group used more elaborate associative strategies compared to the ASD group and showed better performance in establishing meaning for the non-meaningful materials.

Conclusions:  Results extend and replicate prior findings on memory in ASD. Memory difficulties in ASD might be related to difficulties to establish meaning for material to support memory and strategy use might play a role in task performance. Results will be discussed in relation to broader theories about memory functioning in ASD and speculations will be made about underlying cognitive processes.