Background: In addition to core deficits, toddlers with autism spectrum disorders (ASD) experience difficulties with adaptive functioning. Adaptive functioning, therefore, is often a target of intervention. However, the relationship between adaptive functioning deficits, IQ, and autistic symptomatology remains unclear. For instance, a study by Liss and colleagues (2001) divided individuals with ASD into high- and low-functioning groups and found that in the high-functioning group only deficits in adaptive behavior were strongly correlated with autistic symptomatology, but that IQ was strongly predictive of adaptive behavior in the low-functioning group. This study and others utilized the Vineland Adaptive Behavior Scales (Vineland) across various ages. To our knowledge, there has been no study to date comparing the Vineland to the Adaptive Behavior Assessment System (ABAS-II) in toddlers with ASD.
Objectives: The objectives of our study are two-fold. The first is to clarify the relationships outlined above and to compare the new edition of the Vineland to another measure, the ABAS-II. The second is to extend the age-range downward from that reported in previous studies, by comparing these two measures in a group of 3-year olds with and without ASD.
Methods: To date, we have studied 28 toddlers (21 males, 7 females; mean age = 38.64 months, SD = 2.95). All children were recruited as part of the Infant Brain Imaging Study (IBIS). At the age of 3, diagnostic status is confirmed using clinical judgment, taking into account developmental (Mullen Scales of Early Learning (MSEL) and adaptive functioning (Vineland-II), ADOS, and ADI-R. For the purposes of these preliminary analyses, participants were grouped into ASD (n = 9) versus Non-ASD (n = 19), but participants will be stratified by specific autism diagnosis, as well as by specific developmental delay in our final analyses. Total, standard, and calibrated scores from multiple measures will be used to compare these toddlers.
Results: Not surprisingly, a comparison of means across the MSEL, ABAS, and Vineland revealed that in general the Non-ASD group performed better than the ASD group. Using one-way ANOVA, significant differences were found between groups on certain domains of these three measures, but not all. In our limited sample of toddlers diagnosed with ASD, partial correlations revealed strong positive associations between the Composite scores of both the Vineland-II and the ABAS-II, both with and without controlling for developmental functioning. In contrast, in our small sample of Non-ASD toddlers, these measures were not correlated with one another. We will examine these differences as we continue to accrue participants and future analyses will take into account severity of symptom expression as well as the correlations between measures on our sample of Non-ASD toddlers.
Conclusions: Our preliminary analyses demonstrate that in a small group of children diagnosed with ASD, the Vineland-II and ABAS-II are highly positively correlated. These results suggest that either measure of adaptive functioning will appropriately capture these important daily functions. A detailed understanding of these relationships in toddlers should clarify (a) profiles of adaptive behavior difficulties in ASD; and (b) differences in these two commonly used measures.
