Dominic is left-handed. He would like to know if his infant son is likely to be left-handed or right-handed. What can you tell him about the roles of nature and nurture in handedness?

Question

What will be an ideal response?

Answer 1

Research on handedness supports the joint contribution of nature and nurture to brain lateralization. Handedness reflects the greater capacity of one side of the brain—the individual's dominant cerebral hemisphere—to carry out skilled motor action. Other important abilities are generally located on the dominant side as well. For right-handed people—in Western nations, 90 percent of the population—language is housed in the left hemisphere with hand control. For the left-handed 10 percent, language is occasionally located in the right hemisphere or, more often, shared between the hemispheres. This indicates that the brains of left-handers tend to be less strongly lateralized than those of right-handers.
Left-handed parents show only a weak tendency to have left-handed children. One genetic theory proposes that most children inherit a gene that biases them for right-handedness and a left-dominant cerebral hemisphere. But that bias is not strong enough to overcome experiences that might sway children toward a left-hand preference. Even prenatal events may profoundly affect handedness. The orientation of most fetuses—facing toward the left—is believed to promote greater motor control on the body's right side. Handedness also involves practice. It is strongest for complex skills requiring extensive training, such as eating with utensils, writing, and engaging in athletic activities. And wide cultural differences exist.