CONSCIOUSNESS AND COMMISSUROTOMY .6. EVIDENCE FOR NORMAL DUAL CONSCIOUSNESS

This article addresses the problem of evidence for Puccetti's hypothes is of normal dual consciousness, i.e., the hypothesis that a stream of consciousness flows in each cerebral hemisphere when both are functio ning normally in intact, healthy people. Evidence counts as supportive only if it is not explainable by a certain close alternative hypothes is that holds consciousness to proceed in the nondominant hemisphere o nly when the dominant hemisphere is unable to inhibit it (e.g., comple te commissurotomy, dominant hemispherectomy, dominant anesthesia). Fro m this perspective, I discuss (a) two experiments involving anesthesia of the dominant hemisphere that were proposed, respectively, by Wilso n and Puccetti, (b) an actual experiment on normal, unanesthetized sub jects reported by Landis, Graves, and Goodglass, as well as (c) a furt her kind of experiment which, I suggest, may discriminate between the hypotheses. Assuming Puccetti is right, this experiment should yield a distinct pattern of reports from the dominant hemisphere about its ex periences of acting as the individual deals with different kinds of ta sks (''nondominant'' vs. ''dominant''). Also considered is the common (negative) introspective evidence to the effect that we have only a si ngle stream, never two distinct experiences at the same time. I argue, in support of Puccetti, that this is as it should be because introspe ction-at-a-distance is impossible; privileged access is internal to a stream, never occurs between streams.