Final answer:
Split-brain research shows that the two cerebral hemispheres have specialized functions, and when separated, can cause unique behavioral manifestations, like the inability to verbally identify an object in the left visual field. These findings challenge popular misconceptions about hemispheric dominance and contribute to our understanding of brain lateralization and language evolution.
Step-by-step explanation:
The work with alien-hand patients and Sperry's research with split-brain patients indicate that we may all have a second, irrational aspect within us, a result of the unique functions of our cerebral hemispheres. When the connection between the two hemispheres, the corpus callosum, is severed to treat conditions like intractable epilepsy, each hemisphere operates independently. This can manifest as the inability to verbally name an object seen in the left visual field because the sensory information is processed in the right hemisphere, which is typically non-dominant for language. Therefore, the left hemisphere, which houses the speech center in most individuals, remains uninformed of the object.
This condition, known as split-brain, provides valuable insights into cerebral functions and lateralization of brain activity. It challenges popular misconceptions about the left brain and right brain dominance in people and shows the complexity of hemispheric specialization. Additionally, it also raises questions about how manual gestures and language evolution are interconnected, a topic explored further in Michael Gazzaniga's book The Truth About Language.