A Distinction Between Verbal and Nonverbal Working Memory in Children with Asperger Syndrome

Background:   The term working memory (WM) refers to a mental workspace, or a temporary form of memory that involves the ability to maintain and manage novel information long enough to accomplish a task.  WM capacity is thought to be an important predictor of an individual’s learning potential.  Difficulty with this ability can lead to a wide range of encoding and retrieval deficits.  Previous studies have demonstrated that individuals with autism show some deficits with WM capacity, particularly in the verbal domain.  Since individuals with Asperger Syndrome typically demonstrate greater strengths in the verbal domain relative to the nonverbal domain, we predicted that they would show a reversed trend with respect to WM capacity than individuals with autism.
Objectives: To examine verbal and nonverbal WM in children with Asperger Syndrome.
Methods:   Participants included 13 children diagnosed with Asperger Syndrome, and 13 age-, gender- and IQ-matched control participants. Verbal WM was assessed using the Digit Span test and nonverbal WM using the Self-Ordered Pointing Task.
Results: Consistent with previous studies of autism, children with Asperger Syndrome showed impaired performance on verbal, but not the nonverbal WM task.
Conclusions: Although this finding contradicted our hypothesis, qualitative observations and post-task interview revealed greater use of verbal strategies during the nonverbal task by children with Asperger Syndrome.  Thus, verbal reasoning abilities may have masked possible deficits in nonverbal WM capacity.  Future studies should apply more sensitive spatial working memory tasks.  Results are discussed with respect to compensatory techniques applied by individuals with Asperger Syndrome and implications for development of remediation techniques.