“Now, if the person has an intact corpus callosum, the information is almost immediately available to the left hemisphere as well, having passed through the corpus callosum to get there. However, if the person is a split-brain patient, then the information, a picture of a pear, stays in the right hemisphere.”

“Now it gets tricky,” the professor says, “because Broca’s area, which is responsible for speech, is on the left side of the brain. So the split-brain patient can’t tell us what he’s seen. In fact, if we ask him what he saw, he’ll say something like ‘I don’t know’ or ‘I didn’t see anything,’ because the left hemisphere answers the question.

“But just because it can’t say anything, that doesn’t mean the right hemisphere can’t tell us what it saw. If we ask the patient to pick the seen object from a group of objects behind the screen, as you can see, the left hand picks the pear. By contrast, the right hand picks the wrong object. Why do you think this is?”