Sever the cable between your brain's two halves, and each side can want different things

In the 1960s, Roger Sperry and Michael Gazzaniga studied 'split-brain' patients whose corpus callosum had been cut to treat severe epilepsy. Flash a word to only the left eye and a patient could draw what it named but not say it aloud — proof each hemisphere can act, and even want, on its own.

— Roger W. Sperry, Some Functional Effects of Sectioning the Cerebral Commissures in Man — Proceedings of the National Academy of Sciences, 1968