Familial handedness and sex differences in strength of hand preference.

Handedness inventory scores and details of familial handedness were obtained for 54 males and 71 females. For males the handedness distributions of subjects with and without familial sinistrality (FS) did not differ significantly. For females more extreme handedness scores were observed for subjects with FS in both left and right handed ranges of the handedness distribution. Sex differences in handedness were apparent only in subjects with FS, where females displayed more extreme scores at both ends of the distribution. These results are discussed in terms of possible genetic, environmental and other influences on the expression of manual asymmetry and it is concluded that at present we have insufficient information to be able to adequately explain variations in handedness in terms of one or more such influences.