Simultaneous double discrimination response following brain bisection

The performance of two choice reactions, one with each hand, in response to two visual discrimination tasks presented simultaneously, one in each half of the visual field, normally takes much longer than the performance of either one alone. In commissurotomized human patients, however, the double task was performed as rapidly as the single task. The results conform with the view that the neocortical commissures serve to unify adjustment to the visual world (Gazzaniga et al, 1965) and their presence tends to prevent the two half brains from making discordant volitional decisions.