Objective Episodic memory has been shown to be impaired in the autistic population. Therefore, the current study aims to systematically review the literature of episodic memory deficits in autism spectrum disorder (ASD) using meta-analytic statistical techniques to quantify the magnitude of this effect and examine the reliability across aggregated studies. Method: A search of relevant literature within ‘PsycINFO’ and ‘Scopus’ databases yielded 23 studies that met criteria for analysis. Articles were included according to the following criteria: (1) published between 2000 and 2015; (2) compared episodic memory in individuals with clinically diagnosed high-functioning ASD and typical-developing controls; and (3) reported statistics such as means and standards deviations to calculate standardized mean difference effect sizes. The 23 studies represented a total of 518 individuals with high-functioning ASD and 547 age-matched healthy controls. Weighted Cohen's d effect size estimates and confidence intervals were calculated for episodic memory. Results: A random-effects model was used for the meta-analysis, consistent with the significant heterogeneity in the data (Q = 119.58, p < .05). The results of the analysis revealed a pooled effect size estimate (Cohen's d) of −1.00, 95% CI [−1.39, −0.62], a large effect size. Conclusion: The analysis has quantified the magnitude of the effect ASD has on episodic memory across multiple studies. The results suggest that episodic memory deficits are present and of a large magnitude in the ASD population, but heterogeneity in episodic memory was observed across studies. Further research should examine potential moderators that explain the variability across samples.
Immediate List Recall as a Measure of Short-Term Episodic Memory: Insights from the Serial Position Effect and Item Response Theory