Evidence for an attraction account of closing-in behaviour.

"Closing-in behaviour" (CIB) is a phenomenon observed on copying and imitation tasks, in which the copy is made inappropriately close to or on top of the model. CIB is classified clinically as a manifestation of constructional apraxia (CA), but its underlying causes are not understood. Compensation hypotheses propose that CIB is a strategic adaptation to underlying deficits in visuospatial and/or memory functions. The attraction hypothesis suggests that CIB reflects a primitive default behaviour in which the acting hand is drawn towards the focus of visual attention. We tested between these hypotheses in a 62-year-old woman with moderate Alzheimer's disease precipitating CA and apraxia, who showed marked CIB in graphic copying and gesture imitation. We presented two dual tasks: In the first, a straight-line drawing task was combined with a letter-reading task; in the second, simple gesture production was combined with a letter-reading task. In each case, the patient's productions deviated markedly towards the location of the reading task. These data provide strong support for the attraction hypothesis and show that CIB is not specific to copying.