A Comparison of the Instruments that Assess Language and Communication in Students with Autism Spectrum Disorders and an Analysis of Their Functional Uses
Previous research indicates that children with autism spectrum disorder (ASD) receive a different mental age equivalent score for each language instrument administered although these assessments are used interchangeably in the literature. This study analyzed test variables, content, and information load of four language and communication instruments (Vineland Adaptive Behavior Scales: Interview Edition – Expanded Form (VABS-CD) Reynell Developmental Language Scale (RDLS), Preschool Language Scale – Fourth Edition (PLS-IV), and the General Language Composite from the Wechsler Preschool and Primary Scale of Intelligence – Third Edition (GLC)) commonly used with children diagnosed with ASD. Results indicated that the instruments differ significantly in format, administration procedures, materials, and suggested uses. Additionally, the assessments differ in the content balance of communication versus language, with all four assessments measuring mainly language with few or no communication items. Although the balance of receptive and expressive items varied, the discrepancies were minimal. Content classification into areas of language and communication revealed differences in the emphasis placed on the various subsystems. Lastly, information load was analyzed to determine the number of factors to be processed in a given instruction for a correct response. The tests also differ greatly on this factor. Ultimately, these results indicate that the RDLS is more complex due to the combination of the high information load with the percentage of items categorized as deficiencies for children with ASD. The implications of instrument differences when evaluating children with autism are discussed and recommendations provided for practitioners and researchers utilizing these instruments.