The measurement of handedness by preference and performance tests.

Hand preference and hand proficiency were compared on 50 male subjects (30 self-classified left-handers and 20 self-classified right-handers) according to their responses to a 20 item questionnaire and their performances on a handwriting and a grip-strength task. Performance differences between the two sides for each group were not related to overall preference assessments but were positively associated with hand preferences on corresponding questionnaire items. Distributions of the performance differences between the two sides for the right- and left-handers were well separated for handwriting but completely overlapped for grip strength. Significant correlations between the performances on each side were recorded on both tasks. The results stress the importance of using the same criteria in making preference vs. performance comparisons and highlight the need to recognize and control the influence of previous training or experience.