Developmental vision determines joint action control

Vision plays a crucial role in defining external reference frames to organize and optimize action control. While recent findings showed that developmental vision fun-damentally changes the default use of reference frames from anatomical – congenitally blind – to external coordinates – late blind and sighted (Röder, Kusmierek, Spence, & Schicke, 2007, PNAS, 104, 4753–58), surprisingly little is known about the role of vision in jointly interacting  individuals. Here, we tested whether developmental vision also changes referential framing during joint action. To that end, pairs of congenitally blind, blindfolded sighted, and seeing individuals (all groups matched in terms of age, gender, and handedness) performed an auditory joint go-nogo Simon task in a crossed and uncrossed hand condition. Results showed joint go-nogo Simon effects (joint cSEs) in all groups when participants’ hands were uncrossed: Responses were significantly faster when target stimulus and assigned response corresponded as compared with when they did not. More importantly, when performing the joint go-nogo Simon task with crossed hands, the joint cSE disappeared in the congenitally blind, but not in the blindfolded or seeing groups (Fig. 7.1.3). Whereas the compatibility of stimulus-response location led to faster responses in the blindfolded sighted and seeing irrespective of hand position, this facilitation effect disappeared in congenitally blind people when hands were crossed. Based on recent findings, we take this result to suggest that congenitally blind individuals automatically represent spatial information in an anatomical reference frame (e.g. with respect to their hand). Under crossed-hand conditions, this representation needs to be recoded in external coordinates, leading to prolonged reaction times. Sighted people, in contrast, preferably code space by using an external reference frame which is unaffected by positional changes of the effector. Extending previous findings, the present results imply that developmental vision determines the reference frames not only in individual but also in joint action control.