Volume 6 (2008) Pages 113-119
This study aimed to examine the characteristics of handedness in Japanese adults based on gender differences, the presence of left-handed (LH) relatives and experiences with the forced conversion of handedness. Subjects were comprised of 4668 Japanese adults ranging from 15 to 29 years of age (3127 males 18.8±1.8 years old and 1541 females 18.8±1.4 years old). We investigated their subjective handedness, the presence and type of LH relatives, and their experiences with forced conversion of handedness. Although there was no gender difference in the incidence of “innate LH (a subject who had experienced forced conversion of handedness, or a LH subject without experience in the forced conversion)”, females underwent more forced conversion of handedness and had a higher incidence of subjects whose handedness changed from LH to RH. There was no significant difference in the proportion of forced conversion based on the presence of LH relatives, but the incidence of innate LH was higher in subjects with LH relatives and the proportion of LH subjects who remained unchanged after forced conversion was also higher in subjects with LH relatives. Among the subjects with LH relatives, the incidence of current LH was significantly higher in subjects with LH grandparents or parents than siblings. These findings may suggest that forced conversion may influence a gender difference in the incidence of LH. In addition, the presence of LH relatives genetically and environmentally (imitation) influences handedness, and the influence is greater in parents than siblings.