The Ability to Use a Picture As a Symbol in Children with ASD
Objectives: In this study, we first compared referential understanding of pictures between children with ASD and a control group of typically developing children. Second, we studied the influence of iconicity on symbolic picture use. Third, we explored possible associations with chronological age, nonverbal mental age, response to joint attention, language skills, and severity of ASD.
Methods: We compared a group of 28 children with ASD (ASD-group) to 28 typically developing children (TD-group) individually matched on nonverbal mental age (2-5 years). Diagnosis of ASD was confirmed by using the ADOS. The use of pictures as a symbol was based on an object retrieval procedure with pictures developed by DeLoache (1991) and adapted by Bebko, McCrimmon and McFee (McFee, 2006). Pictures with varying degrees of iconicity were used to study the influence of visual resemblance on the symbolic picture use.
Results: Overall, children with ASD achieved lower levels of pictorial competence on the symbolic search tasks than the control group (X2(1) = 9.22, p = .002). More than half of the children with ASD (57%) did not understand and use the pictures in a symbolic way, compared to only 18 percent in the control group. The children with ASD were less successful than the comparison groups on most of the symbolic retrieval tasks (p < .05). However, the variance in scores was much higher in the ASD-group. In the ASD group, the scores on the different tasks were comparable (F(2,54) = 0.20, p = .82), whereas in the control group, a small influence of iconicity was found (F(2, 54) = 2.64, p = .08). There is a clear relationship between nonverbal mental age and errorless retrievals in the TD-group (r(26) = .78, p < .001), with strong increase in errorless retrievals between 24 and 30 months. The correlation is also significant in the ASD-group (r(26) = .79, p < .001), but the pattern is different in comparison with the control group. After controlling for nonverbal mental age, several other skills are related to performance on the symbolic search tasks in the ASD group, such as response to joint attention, receptive and expressive language, and severity of ASD characteristics.
Conclusions: One of the main conclusions to be drawn from this study is that children with ASD have more difficulties in understanding and using pictures in a symbolic way compared to the control group. The most common communication strategies, naturalistic as well as augmentative, presume symbolic abilities. The findings from the current study suggest that clinicians would benefit from evaluating symbolic understanding of pictures, especially in young, lower functioning or minimally verbal children with ASD.