Evidence in bimanual finger-tapping of an attentional component to stuttering.

The performance of right- and left-handed male and female stutters was compared with that of non-stutters on a bimanual coordination task that involved tapping a key twice with one hand for each single tap of a key by the other hand. Right-handed non-stutters performed this 2:1 tapping better when it was the right hand that tapped twice (R2/L1 condition) rather than the left hand (L2/R1 condition), but among left-handers performance was similar under the two conditions. This replicated previous findings of Peters10 that were interpreted as indicating the role of attentional mechanisms in the expression of handedness. The performance of the stutters differed in two major respects. First, overall bimanual tapping rates were significantly slower than those of the non-stutters. Second, right-handed stutters did not show the asymmetry in performance between the R2/L1 and L2/R1 conditions. The results are interpreted within the framework of current neuropsychological research that relates stuttering to anomalous mechanisms of interhemispheric communication.