RETRIEVAL PRACTICE Take a moment to answer each of these Learning Objective Questions (repeated here from within this section). Then click the 'show answer' button to check your answers. Research suggests that trying to answer these questions on your own will improve your long-term retention (McDaniel et al., 2009).

The cerebral cortex has two hemispheres, and each hemisphere has four lobes: the frontal, parietal, occipital, and temporal. Each lobe performs many functions and interacts with other areas of the cortex.
     The motor cortex, at the rear of the frontal lobes, controls voluntary movements. The somatosensory cortex, at the front of the parietal lobes, registers and processes body touch and movement sensations. Body parts requiring precise control (in the motor cortex) or those that are especially sensitive (in the somatosensory cortex) occupy the greatest amount of space.
     Most of the brain’s cortex—the major portion of each of the four lobes—is devoted to uncommitted association areas, which integrate information involved in learning, remembering, thinking, and other higher-level functions. Our mental experiences arise from coordinated brain activity.

If one hemisphere is damaged early in life, the other will pick up many of its functions by reorganizing or building new pathways. This plasticity diminishes later in life. The brain sometimes mends itself by forming new neurons, a process known as neurogenesis.

Split-brain research (experiments on people with a severed corpus callosum) has confirmed that in most people, the left hemisphere is the more verbal, and that the right hemisphere excels in visual perception and the recognition of emotion. Studies of healthy people with intact brains confirm that each hemisphere makes unique contributions to the integrated functioning of the brain.

Some 10 percent of us (somewhat more among males, somewhat less among females) are left-handed. Handedness appears to be influenced by genetic or prenatal factors. Most left-handers process speech in the left hemisphere, as right-handers do, but some do so in the right hemisphere or use both hemispheres. Left-handers are more likely to be among those with reading disabilities, allergies, and migraine headaches, but sometimes do better academically. Left-handedness is also more common among musicians, mathematicians, architects, artists, and in professional baseball and cricket players. The pros and cons of being left-handed seem roughly equal.