His “party trick” is to draw two separate objects (one with each hand) simultaneously. More than thirty years of research with divided-brain patients has convinced researcher Michael Gazzaniga that asymmetry is the key to understanding our mental capacities. Gazzaniga maintains that intelligence comes from the left hemisphere. The preoperative IQ and problem-solving skills of the split-brain person are the same as that of his left hemisphere after surgery. In contrast, states Gazzaniga, the right hemisphere is “sort of dumb.” However, in comparison to the right hemisphere, the left hemisphere is poor at recognizing visual patterns. Even a mouse brain is able to discriminate between the two visual patterns that Joe's left hemisphere fails to distinguish. Gazzaniga speculates that, as part of the process of evolution, the left hemisphere mutated to develop language. As a result, its complex, perceptual processes were squeezed out and became the province of other brain areas. In the course of evolution, he concludes, our left hemisphere acquired more complex cognitive functions, while our right hemisphere remained largely unchanged.