A Comparison of Basic Attentional Shifting Between Adults and Children with High Functioning Autism

Background: The debate continues as to whether individuals with autism have a fundamental deficit in attentional shifting and whether this deficit contributes to their poor performance in executive function tasks (Kleinhans et al., Developmental Neuropsychology, 2010).  Attention shifting in autism has been studied with a variety of tasks, including simple measures using shifting between perceptual modalities and other measures that require complex conceptual reasoning, with a range of results. Differences in attentional shifting between children and adults with autism have received less attention.

Objectives: This study evaluated whether there is a difference between children and adults with high-functioning autism (HFA) in basic attentional shifting using a simple task, the modality shift reaction time experiment, that involves minimal reasoning, decision-making, or related information processing components.

Methods: Participants were 33 children and 42 older adolescents and adults with HFA and comparison groups of equal numbers of typically developing individuals matched on age, gender, and IQ. Stimuli were a red light, a green light, a high tone, and a low tone presented in ipsimodal (light-light; sound-sound) and contramodal (light-sound; sound-light) sequences responded to by a button press. Normal individuals respond more slowly to the second member of contramodal than to the ipsimodal sequences reflecting a deficit in attention to a changed modality or a modality shift effect (MSE), but individuals with psychopathology produce an exaggerated delay. The measure of specific interest is, therefore, the relationship between contramodal pairs and ipsimodal pairs or the MSE.

Results:  The adults with autism exhibited slower reaction times to lights and sounds than the typical controls. The children with autism exhibited slower reaction times to light. There were no significant modality interactions in the adults with HFA, indicating the absence of a significant exaggerated MSE in this group. This finding in the adults with HFA may be the consequence of their slower reaction times to sound and light. There were two significant interactions in the child comparison, both in the condition involving reaction time to a sound followed by a light, indicating an exaggerated MSE in children with HFA.

Conclusions: A significant MSE for a sound followed by a light was found in children but not adults with HFA. Therefore, the MSE appears to be a developmental phenomenon found in children but not adults in this population. In adults with HFA, the MSE appears to merge into a more generalized psychomotor slowness.