Handedness classification: preference versus proficiency.

Relative hand preferences as indicated by questionnaire were compared with asymmetries in manual proficiency at three levels of task difficulty (N equal to 63 adults). Correlations between odd/even trial relative hand proficiency scores were .887 and .879 attesting to their stability. Test-retest (6-wk. interval) reliabilities for relative hand proficiency ranged from .831 to .893. Spearman rbos between the questionnaire responses and relative hand proficiency were .733, .689, and .619. These relatively low relationships, especially at the highest level of task difficulty (r2 = 38%), indicate that hand preference does not reflect relative hand proficiency at moderate to high levels of task difficulty.