There is/was a whitening toothpaste called Rembrandt. In a competitor's ad they made the claim, "Even Rembrandt can't beat it!". They wanted you to hear that it was better than Rembrandt, but they were actually saying it was equivalent.
Right, in callosotomy patients there's some level of information exchange via secondary pathways. In particular, one of Gazzaniga's experiments showed transfer of emotions.
Last year I watched Dr. Gazzaniga's 2009 Scotland lecture series on Youtube. I noticed an inconsistency that bothered me enough to email him, but never got a reply.
In his third Edinburgh video lecture[1], he shows two videos featuring patient J.W.
In the second video, the test flashes RED and BANANA to his left and right hemispheres, respectively, and J.W. is asked to draw what he sees. He then proceeds to pick up the red pen with his left hand. But, the hand's controlling hemisphere only saw BANANA. How did it decide to pick up the red pen?
Similarly, in the first video, the words MUSIC (L) and BELL (R) are flashed. He's asked to point to a picture of what he saw and he uses his right hand to point to BELL, but its controlling hemisphere only saw MUSIC.