Normal distribution of hand preference and its bimodality.

Abstract

The distribution of hand preference was studied in human subjects by means of The Waterloo Handedness Questionnaire and Edinburgh Handedness Inventory. The Waterloo Handedness scores (WS) and Geschwind Scores (GS) were estimated. Left-handers (WS < 0; GS < 0) and right-handers (WS > 0; GS > 0) constituted separate groups (dichotomy). The WSs, and to a lesser extent GSs, were distributed normally when only the right-handers were considered. There was a significant positive-linear correlation between WSs and GSs. These results suggested that a detailed questionnaire such as the Waterloo Handedness Questionnaire would be more appropriate than concise questionnaires in assessing hand preference. A normally distributed right-hand preference and a widely dispersed left-hand preference also supports the concept of anomalous dominance for left-handedness.