Evaluation of executive functioning in people with intellectual disabilities

Abstract

Executive functioning (EF) is an important concept in cognitive psychology that has rarely been studied in people with intellectual disabilities (IDs). The aim of this study was to examine the validity of two test batteries and the structure of EF in this client group. We administered the children's version of the Behavioural Assessment of the Dysexecutive Syndrome (BADS-C) and the Cambridge Executive Functioning Assessment (CEFA) for people with ID, to 40 participants who attended day centres for people with mild to moderate learning disabilities [mean full-scale intelligence quotient (IQ) = 59]. The BADS-C consists of six EF subtests while the CEFA contains eight EF (including two executive memory) subtests and four memory subtests. IQ and receptive language ability were also assessed. The results were subjected to principal components analysis, and regression analysis was used to examine the relationship of the ensuing factors to other cognitive variables. Scores on both sets of EF tests were only weakly related to receptive language ability, and even more weakly related to IQ. Scores on the BADS-C were substantially lower than predicted from the published norms for people in higher IQ ranges, and many participants scored zero on three of the six subtests. This potential floor effect was less evident with scores on the CEFA. Principal components analyses produced one usable factor for the BADS-C, and two factors for the CEFA that differed in both the extent of involvement of working memory and the predominant sensory modality. A combined analysis of the subtests retained from both analyses produced three factors that related uniquely to aspects of IQ and memory. The CEFA is suitable for use with people with mild to moderate learning disabilities, whereas the BADS-C is at the lower limit of usability with this client group. The lower-than-expected scores observed on the BADS-C may indicate that people known to learning disability services may be more impaired than people of comparable IQ not known to services. The structure of EF seen in people with IDs closely resembles a model of EF in the general population that has received a broad level of support.