The corpus callosum had been cut in monkeys and in several other laboratory species, but the animals seemed no different after the surgery than they had been before. Similarly, human patients who were born without a corpus callosum or had it damaged seemed quite normal (see Paul et al., 2007). In the early 1950s, Roger Sperry, whom you may remember for the eye-rotation experiments described in Chapter 9, and his colleagues were intrigued by this paradox.