Illness and accidental injury in young and older adult left- and right- handers: Implications for genetic theories of hand preference

Three age groups (N = 387) of self-classified left- and right-handers - young adults (ages 18 to 30 years), older adults (ages 55 to 74 years) and oldest old adults (ages 75 to 94 years)-answered questions concerning their health and accident occurrence history. We found no evidence to support the suggestion that left-handers were more likely to suffer from either major or minor health problems, including categories of illnesses associated with immune disorders. Also, the left-handed groups did not display a significantly higher incidence of either major or minor accidental injury, although they indicated that they found common cutting implements less easy to use when compared to the responses of right-handers. Left-handed participants in all 3 age groups indicated that attempts had been made, typically during their childhood years, to switch their hand preference toward the right side; the highest incidence rate of switch reports was among the oldest old adult left-handers, with 82.6% reporting hand preference change attempts. Our data are not consistent with models of hand preference formation that state that deviations from genetic fight-hand preference are the complete or partial result of pathological influences (Coren, 1995b). However, our data can be incorporated into genetic models that take into account the influences of life experience variables on hand preference formation (Laland, Kumm, Van Horn, and Feldman, 1995).