Something Sinistral Going On? Asymmetry in Arm Movement Frequency

In a test of the hypothesis that the dominant arm would be more active than the nondominant arm, 70 young adults (including 34 left-handers) wore instrumented motion recorders on both wrists for 48 hours. Participants' left arms made approximately 80 more movements per hour than did their right arms, which was unexpected. This mean difference reflected a generalised leftward shift in the distribution of the frequency of arm movements. Two-thirds of the individuals in the sample were characterised by a sinistral bias in arm movement frequencies. Degree of sinistral bias in arm movement frequency was unrelated to hand preference as measured by the Waterloo Inventory. Implications of this new asymmetry are discussed.