HANDEDNESS TRENDS ACROSS AGE-GROUPS IN A JAPANESE SAMPLE OF 2316

Hand-preference data of 2316 Japanese were analyzed by age groups, sex , and familial sinistrality. Right-hand preference increased across ag e groups at least up to 30 years for men, while women showed relativel y stable and stronger preference for right-hand use. Unlike some Weste rn studies, no linear trends across age groups were found for both sex es. Declining cultural censorship against left-handedness would not be responsible for the trends, since there was no evidence indicating su ch a decline in Sapan. Hypotheses of reduced longevity and life-long a daptation to the right-handed world are not satisfactory either, since both hypotheses assume a linear trend spanning the entire life span. Thus, it seems that a single-factor hypothesis which explains all the results by resorting to a single cause does not account for the comple x results found in this and other studies.