Meta-analysis of explicit memory studies in populations with intellectual disability

This meta-analysis combines the effect size (ES) of 40 explicit memory experiments in populations with intellectual disability (ID). Eight meta-analyses were performed, as well as contrast tests between ES. The explicit memory of participants with ID was inferior to that of participants with typical development (TD). Relatively preserved explicit memory performance was found among participants with Williams syndrome compared with participants with TD and with Down syndrome. The mean ES between the groups with ID vs. TD, when control group selection was based on chronological age, was greater than when comparison was based on mental age. There was no difference in the ES between recall and recognition tests. Verbal memory was more impaired than visual memory.