Left-handedness and age: comparing writing/ drawing and other manual activities.

The percentage of individuals who use the left hand for writing/drawing, brushing teeth, and throwing a ball was compared in 3229 subjects ranging in age from 8 to 96 years. The "elimination" versus "modification" hypotheses were tested as explanations of prior observations that there are fewer left-handers among the elderly. These hypotheses predict different numbers of left-handed elderly individuals when measured by activities not influenced by social pressure. The results suggest that there are age-related patterns among different measures of left-handedness. However, a significant decline in left-handedness among the elderly was also found when measured by less culturally determined activities.