Memory in Autism Spectrum Disorder: A Meta-Analysis of Experimental Studies

To address inconsistencies in the literature on memory in autism spectrum disorder (ASD), we report the first ever meta-analysis of short-term memory (STM) and episodic long-term memory (LTM) in ASD, evaluating the effects of type of material, type of retrieval and the role of interitem relations. Analysis of 64 studies comparing individuals with ASD and typical development (TD) showed greater difficulties in ASD compared with TD individuals in STM (Hedges' g = -0.53, 95% CI [-0.90, -0.16], p = .005, I-2 = 96%) compared with LTM (g = -0.30, 95% CI [-0.42, -0.17], p < .00001, I-2 = 24%), a small difficulty in verbal LTM (g = -0.21, p = .01), contrasting with a medium difficulty for visual LTM (g = -0.41, p = .0002) in ASD compared with TD individuals. We also found a general diminution in free recall compared with cued recall and recognition (LTM, free recall: g = -0.38, p < .00001, cued recall: g = -0.08, p = .58, recognition: g = -0.15, p = .16; STM, free recall: g = -0.59, p = .004, recognition: g = -0.33, p = .07). We discuss these results in terms of their relation to semantic memory. The limited diminution in verbal LTM and preserved overall recognition and cued recall (supported retrieval) may result from a greater overlap of these tasks with semantic long-term representations which are overall preserved in ASD. By contrast, difficulties in STM or free recall may result from less overlap with the semantic system or may involve additional cognitive operations and executive demands. These findings highlight the need to support STM functioning in ASD and acknowledge the potential benefit of using verbal materials at encoding and broader forms of memory support at retrieval to enhance performance.