P e r c e p t d and Motor Shills, 1977,45, 1041-1042. @ Perceptual and Motor Skills 1977
HANDEDNESS CLASSIFICATION : PREFERENCE VERSUS PROFICIENCY JOHN I. TODOR AND THOMAS DOANE University of Michigan Summary.-Relative hand preferences as indicated by questionnaire were compared with asymmetries in manual proficiency at three levels of task difficulty ( N = 6 3 adults). Correlations between odd/even trial relative hand proficiency scores were 3 8 7 and .879 attesting to their stability. Test-retest (6-wk. interval) reliabilities for relative hand proficiency ranged from 3 3 1 to 393. Spearman rhos 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 (1.a = 3 8 % ) , indicate that hand preference does not reflect relative hand proficiency at moderate to high levels of task difficulty. In spite of numerous investigations the extent to which hand preference reflects hand proficiency remains controversial. Barnsley and Rabinovitch (1970) among others (Benton, Meyers, & Polder, 1962; Palmar, 1974; Provins & Cunliffe, 1972) have reported relatively low relationships between hand preference and hand proficiency and/or substantial discrepancies in classification. On the other hand, Annett (1970) suggested that a linear relationship exists between relative preference and relative manual skill. However, her own data indicate discrepant classification among the less extreme preference groups. Recently a moderately high correlation of .78 was reported by Lake and Bryden ( 1976) between a handedness questionnaire and a visually guided repetitive manual aiming task. The above mentioned inconsistency between hand preference and manual proficiency may be due, in part, to inherent measurements problems. For example, Steingruber ( 1975 ) demonstrated that the distribution of performance asymmetries changes with changes in task complexity, the most pronounced and stable hand dominance being observed on demanding criterion tasks. Since hand-preference measures rely on simple overlearned tasks subject to incidental or social learning, they probably result in competence only in low skill level tasks. This is crucial since the composition of the left-handed category has been demonstrated to vary up to 30% when different measures are used ( Schwartz, 1977 ) . To resolve this apparent discrepancy between hand preference and hand proficiency the stabiIity of asymmetry in manual proficiency was assessed at three levels of task difficulty and correlated with relative hand preference as indicated by questionnaire. Sixty-three adults (37 females, M = 24.64 yr., S D = 2.88 yr.; 26 males, M = 23.28 yr., SD = 2.35 yr.) completed a questionnaire soliciting a preference indication on 8 unimanual and 10 bimanual tasks (Flowers, 1975). The hand-proficiency measure required subjects alternately to tap a stylus on two adjacent targets as rapidly as possible. Through manipulation of width and target distance, the index of difficulty could be increased and quantified (Fitts, 1954). Accordingly, combinations of target distance of 0.5 and 8; 0.5 and 16; and 0.25 and 16 in. produced indices of difficulty of 5, 6, and 7 respectively. Using a counterbalanced design, the mean number of hits for four 10-sec. trials was obtained for each hand at each of the 3 levels of difficulty. Trials were repeated if errors, i.e., the stylus missed the target,
1042
J. I. TODOR
&
T. DOANE
exceeded 10% of the total hits. The direction and magnitude of ,differences in performance between the hands at index of difficulty 7, were designed as the hand-superiority score. Correlations between adjacent hand-superiority scores were .887 (difficulty 5 / 6 ) and .879 (difficulty 6 / 7 ) , attesting to their stability. Test-retest reliability over a 6-wk. interval for the hand-superiority scores of 18 subjects ranged from 3 3 1 to 3 9 3 . Considering the restricted range inherent with the use of difference scores and its effect on the correlation coefficient, the hand-superiority scores appear to be sufficiently stable to warrant their use. Spearman rhos between the questionnaire and hand-superiority of .7 33, .689, and .619 were obtained at indexes of difficulty 5, 6 , and 7 respectively. These relatively low relationships, especially at the highest level of difficulty (12 = 38 a/o ), support the contention that the questionnaire assessment of hand preference does not reflect hand superiority on tasks of moderate to extreme difficulty (questionnaire assessment probably reflects learned preference on simple overlearned tasks). It is suggested that handsuperiority scores be used when the purpose is to assess the significance of functional handedness. REFERENCES ANNETT, M. A classification of hand preference by association analysis. British Journal of Psychology, 1970, 6 1 , 303-321. BARNSLEY,R. H., & RABINOVITCH,M. S. Handedness: proficiency versus stated preference. Percepual alzd Motor Skills, 1970, 30, 343-362. BENTON,A . L., MEYERS,R., & POLDER,G . J. Some aspects of handedness. Psychiatria et Neurologia (Basel), 1962, 144, 321-337. FITTS, P. M. The information capacity of the human motor system in controlling the amplitude of movement. Journul o f Experimental Psychology, 1954, 4 7 , 381-391. FLOWERS, K. Handedness and controlled movement. British Journal of Psychology, 1975,66, 39-52. LAKE, D. A., & BRYDEN,M. P. Handedness and sex differences in hemispheric asymmetry. Brain and Langivage, 1976, 3, 266-282. PALMAR, R. D. Development of differential handedness. Psychological Bivlletin, 1964, 62, 257-272. PROVINS,K. A., & C U N L I F F EP., Motor performance tests of handedness and motivation. Perceptual alzd Motor Skills, 1972, 35, 143-150. SCHWARTZ, M. Left-handedness and high risk pregnancy. Neuropsychologica, 1977, 15, 341-344. H. J. Handedness as a function of test complexity. Perceptzral alzd Motor STEINGRUBER, Skills, 1975, 40, 263-266.
Accepted October 5, 1977.
HANDEDNESS CLASSIFICATION : PREFERENCE VERSUS PROFICIENCY JOHN I. TODOR AND THOMAS DOANE University of Michigan Summary.-Relative hand preferences as indicated by questionnaire were compared with asymmetries in manual proficiency at three levels of task difficulty ( N = 6 3 adults). Correlations between odd/even trial relative hand proficiency scores were 3 8 7 and .879 attesting to their stability. Test-retest (6-wk. interval) reliabilities for relative hand proficiency ranged from 3 3 1 to 393. Spearman rhos 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 (1.a = 3 8 % ) , indicate that hand preference does not reflect relative hand proficiency at moderate to high levels of task difficulty. In spite of numerous investigations the extent to which hand preference reflects hand proficiency remains controversial. Barnsley and Rabinovitch (1970) among others (Benton, Meyers, & Polder, 1962; Palmar, 1974; Provins & Cunliffe, 1972) have reported relatively low relationships between hand preference and hand proficiency and/or substantial discrepancies in classification. On the other hand, Annett (1970) suggested that a linear relationship exists between relative preference and relative manual skill. However, her own data indicate discrepant classification among the less extreme preference groups. Recently a moderately high correlation of .78 was reported by Lake and Bryden ( 1976) between a handedness questionnaire and a visually guided repetitive manual aiming task. The above mentioned inconsistency between hand preference and manual proficiency may be due, in part, to inherent measurements problems. For example, Steingruber ( 1975 ) demonstrated that the distribution of performance asymmetries changes with changes in task complexity, the most pronounced and stable hand dominance being observed on demanding criterion tasks. Since hand-preference measures rely on simple overlearned tasks subject to incidental or social learning, they probably result in competence only in low skill level tasks. This is crucial since the composition of the left-handed category has been demonstrated to vary up to 30% when different measures are used ( Schwartz, 1977 ) . To resolve this apparent discrepancy between hand preference and hand proficiency the stabiIity of asymmetry in manual proficiency was assessed at three levels of task difficulty and correlated with relative hand preference as indicated by questionnaire. Sixty-three adults (37 females, M = 24.64 yr., S D = 2.88 yr.; 26 males, M = 23.28 yr., SD = 2.35 yr.) completed a questionnaire soliciting a preference indication on 8 unimanual and 10 bimanual tasks (Flowers, 1975). The hand-proficiency measure required subjects alternately to tap a stylus on two adjacent targets as rapidly as possible. Through manipulation of width and target distance, the index of difficulty could be increased and quantified (Fitts, 1954). Accordingly, combinations of target distance of 0.5 and 8; 0.5 and 16; and 0.25 and 16 in. produced indices of difficulty of 5, 6, and 7 respectively. Using a counterbalanced design, the mean number of hits for four 10-sec. trials was obtained for each hand at each of the 3 levels of difficulty. Trials were repeated if errors, i.e., the stylus missed the target,
1042
J. I. TODOR
&
T. DOANE
exceeded 10% of the total hits. The direction and magnitude of ,differences in performance between the hands at index of difficulty 7, were designed as the hand-superiority score. Correlations between adjacent hand-superiority scores were .887 (difficulty 5 / 6 ) and .879 (difficulty 6 / 7 ) , attesting to their stability. Test-retest reliability over a 6-wk. interval for the hand-superiority scores of 18 subjects ranged from 3 3 1 to 3 9 3 . Considering the restricted range inherent with the use of difference scores and its effect on the correlation coefficient, the hand-superiority scores appear to be sufficiently stable to warrant their use. Spearman rhos between the questionnaire and hand-superiority of .7 33, .689, and .619 were obtained at indexes of difficulty 5, 6 , and 7 respectively. These relatively low relationships, especially at the highest level of difficulty (12 = 38 a/o ), support the contention that the questionnaire assessment of hand preference does not reflect hand superiority on tasks of moderate to extreme difficulty (questionnaire assessment probably reflects learned preference on simple overlearned tasks). It is suggested that handsuperiority scores be used when the purpose is to assess the significance of functional handedness. REFERENCES ANNETT, M. A classification of hand preference by association analysis. British Journal of Psychology, 1970, 6 1 , 303-321. BARNSLEY,R. H., & RABINOVITCH,M. S. Handedness: proficiency versus stated preference. Percepual alzd Motor Skills, 1970, 30, 343-362. BENTON,A . L., MEYERS,R., & POLDER,G . J. Some aspects of handedness. Psychiatria et Neurologia (Basel), 1962, 144, 321-337. FITTS, P. M. The information capacity of the human motor system in controlling the amplitude of movement. Journul o f Experimental Psychology, 1954, 4 7 , 381-391. FLOWERS, K. Handedness and controlled movement. British Journal of Psychology, 1975,66, 39-52. LAKE, D. A., & BRYDEN,M. P. Handedness and sex differences in hemispheric asymmetry. Brain and Langivage, 1976, 3, 266-282. PALMAR, R. D. Development of differential handedness. Psychological Bivlletin, 1964, 62, 257-272. PROVINS,K. A., & C U N L I F F EP., Motor performance tests of handedness and motivation. Perceptual alzd Motor Skills, 1972, 35, 143-150. SCHWARTZ, M. Left-handedness and high risk pregnancy. Neuropsychologica, 1977, 15, 341-344. H. J. Handedness as a function of test complexity. Perceptzral alzd Motor STEINGRUBER, Skills, 1975, 40, 263-266.
Accepted October 5, 1977.
