Impairment in local and global processing and set-shifting in body dysmorphic disorder

Abstract

Body dysmorphic disorder (BDD) is characterized by distressing and often debilitating preoccupations with misperceived defects in appearance. Research suggests that aberrant visual processing may contribute to these misperceptions. This study used two tasks to probe global and local visual processing as well as set-shifting in individuals with BDD. Eighteen unmedicated individuals with BDD and 17 non-clinical controls completed two global-local tasks. The embedded figures task requires participants to determine which of three complex figures contains a simpler figure embedded within it. The Navon task utilizes incongruent stimuli comprised of a large letter (global level) made up of smaller letters (local level). The outcome measures were response time and accuracy rate. On the embedded figures task, BDD individuals were slower and less accurate than controls. On the Navon task, BDD individuals processed both global and local stimuli slower and less accurately than controls, and there was a further decrement in performance when shifting attention between the different levels of stimuli. Worse insight correlated with poorer performance on both tasks. Taken together, these results suggest abnormal global and local processing for non-appearance related stimuli among BDD individuals, in addition to evidence of poor set-shifting abilities. Moreover, these abnormalities appear to relate to the important clinical variable of poor insight. Further research is needed to explore these abnormalities and elucidate their possible role in the development and/or persistence of BDD symptoms.

Keywords: Body dysmorphic disorder; Embedded figures task; Global-local processing; Navon; Set-shifting.

Fig. 1

Stimuli (a) and sequence of events (b) for the embedded figures task. Participants searched for the shape on the top embedded within one of three complex figures on the bottom.

Fig. 2

Navon stimuli (a) and sequence of events (b). In each trial one of the two targets appeared at either the global or local level accompanied by one of four distractors at the opposite level.

Fig. 3

Speed (a) and accuracy (b) in identifying a simple target shape embedded within a complex figure (embedded figure task – EFT) in the body dysmorphic disorder (BDD) and control groups. The BDD group was significantly slower (p < 0.05) and less accurate (p < 0.01) than the control group.

Fig. 4

Speed (a) and accuracy (b) of processing global and local stimuli (Navon task) in the body dysmorphic disorder (BDD) and control groups.

Fig. 5

Speed (a) and accuracy (b) on the Navon task as a function of maintaining set or switching set between global and local stimuli in the body dysmorphic disorder (BDD) and control groups.

Fig. 6

Speed (a) and accuracy (b) on the Navon task as a function of set condition (GL – global preceded by local; LG – local preceded by global; LL – local preceded by local; GG – global preceded by global) in the body dysmorphic disorder (BDD) and control groups.

Fig. 7

Scatterplots of BABS scores in relation to response times and accuracy rates for the Navon task and the embedded figures task (EFT). P values are shown for general linear mixed model results. *Surviving Bonferroni correction for multiple comparisons.