Consciousness after split-brain surgery: The recent challenge to the classical picture.

A critical evaluation of recent split-brain experiments argues that claims of unified consciousness in patient D.D.C. are premature. Two distinct conceptions of unity of consciousness are distinguished: agency-based and experience-based. Whether the behavioral data demonstrate unity of agency remains an open question, depending on both the mechanisms underlying split-brain behavior and what constitutes a single agent. Even if agency-based unity is established, the data are difficult to reconcile with full unity of consciousness in the experience-based sense.

Study at a glance

Abstract

In a recent series of experiments, Pinto and colleagues found that the split-brain patient D.D.C. was able to respond accurately to stimuli in either visual field, whether using his right hand, his left hand, or verbally. Pinto and colleagues argue that this demonstrates that a split-brain patient remains a unitary agent and thus continues to possess a unified consciousness. This paper provides a critical evaluation of that claim. First, we argue that two conceptions of the unity of consciousness need to be distinguished: an agency-based conception and an experience-based conception. Second, we argue that it is an open question whether the data presented by Pinto and colleagues is best understood in terms of the unity of agency. Whether that interpretation is correct depends not only on the mechanisms that produce split-brain behaviour, but also on what is involved in being a single agent. Third, we argue that even if the behavioral data indicated that D.D.C has a unified consciousness in the agency-based sense of the term, it is difficult to reconcile them with the claim that his consciousness is fully unified in the experience-based sense.