Impaired habituation in children with attention deficit hyperactivity disorder.

OBJECTIVE: To investigate whether children with attention deficit hyperactivity disorder show impaired habituation to peripheral stimuli. METHOD: We compared the Troxler effect (the ability to habituate to a peripheral visual stimulus when presented with a competing central visual stimulus) in groups of 23 children with attention deficit hyperactivity disorder and 15 controls matched for age, gender, and IQ. RESULTS: Regression analyses revealed a statistically significant effect of diagnosis on fading (P = 0.03), with attention deficit hyperactivity disorder subjects taking longer to fade to a peripheral stimulus than controls. Additional analyses revealed a significant interaction between diagnosis and visual field; control subjects showed similar fading times to stimuli presented in the right and left visual fields (13.25 vs. 12.96 seconds), while the attention deficit hyperactivity disorder group showed much slower fading in the right than in the left visual field (18.64 vs. 15.00 seconds). CONCLUSIONS: Our results suggest that children with attention deficit hyperactivity disorder have impaired visual habituation. The findings provide evidence of frontal dysfunction in attention deficit hyperactivity disorder and suggest that impaired habituation contributes to off-task behavior in children with the disorder.