A Reversed Navon Effect In Processing Of Compound Pattern In Children With Attention-Deficit Hyperactivity Disorder

Compound pattern stimuli are widely used to study the relationship between global and local information processing. Since Navon's (1977) studies on global versus local features in perception, the Navon task has also become widespread. Studies examined the role of brain hemisphere activity in the Navon task, and numerous studies have indicated that the processing of global and local information can be attributed to the right and left hemisphere respectively (Delis, Robertson &Efron,1986; Fink et al,1996). Moreover, a substantial body of recent evidence suggests that certain core symptoms of ADHD are related to dysfunction of right hemisphere processes (Vance et al.,2007; Waldiea & Hausmannb,2010; Almeida et al.,2010).If the dysfunction of right hemisphere hypothesis in ADHD is valid, we can predict that global precedence/global interference will be substantially less evident and possibly even be replaced by local precedence/local interference in ADHD, that is the Navon effect may be reversed in children with ADHD. This paper explored on the local precedence and local interference in ADHD, and further examined how the traits of stimulus and individual's character, such as the cognitive flexibility affect Navon effect. The results revealed that:In Experiment 1 and Experiment 2, children with ADHD exhibited local precedence effects, regardless of which attention procedure was used. The finding of excessive local interference LG in ADHD is important, suggesting that children with ADHD process local instead of global information in an automatic manner at a very early stage of processing. The present findings provide direct evidence regarding the nature of the global/local information-processing disturbance in ADHD. Our findings also provide reliable evidence to challenge the deficit hypotheses included in the DSM-â…£(APA,2000), which postulates that ADHD is one of the most common psychiatric conditions of childhood, characterized by symptoms of inattention, hyperactivity, and impulsivity, where inattention may manifest as a failing to pay close attention to details.In Experiment 3, we revealed a local interference effect in children with ADHD. this suggests that the processing to local information may be faster than the processing to global information, thus the local interference occurs.Moreover, in Study 4, Children with ADHD exhibited more reversed Navon effect(local precedence/local interference effect) than controls. However, visual angle contrast affected the local interference in ADHD and the global interference in non-ADHD. As visual angle contrast changed from high contrast (easier to see global information) to low contrast (easier to see local information), the interference ratio also changed, with local interference increasing in ADHD group, and the global interference decreasing in non-ADHD.Finally, in Study 5, cognitive flexibility as measured by WCST was positively related with the score of G and LG as measured by CDCT in ADHD. The regression analysis between the two variables indicated that cognitive flexibility can be used as a parameter to predict the performance on global-directed processing in ADHD.The findings revealed by this preliminary study provide enlightenments to the research regarding the cognitive ability in ADHD and other disorders as well.