Gender, laterality, learning difficulties and health problems.

This paper examines the association between self-reported laterality, learning difficulties and health problems. Responses to questionnaire data were obtained from 3829 males and 3631 females. Males reported increased cardiovascular disease, ulcers, and diabetes. Learning problems were increased in males, nonright-handers and those with a left eye preference. The highest proportion of difficulty learning to read was in males who were nonright-handed and right-eyed. Mixed dominance, however, did not fully explain the results since nonright-handers with left eye preferences had the next highest rate.

A behavioral measure of hand preference as opposed to hand skill.

Twenty-five self-professed left-handers and 21 self-professed right-handers were given a variety of performance tests to assess handedness, along with a preference inventory and a dichotic listening test of language lateralization. The performance tests included the Annett pegboard task, that Tapley and Bryden dot-filling tasks, and two procedures, the long pegboard and long dots tasks, that were intended to assess the point in space at which a particular unimanual movement became sufficiently awkward for one to shift to the other hand. All four of these performance tests differentiated between left-handers and right-handers, although the differences between handedness groups were somewhat larger when handedness was defined in terms of the preference inventory rather than on the basis of self-report. When the difference between preferred and non-preferred hands was examined, the best predictor of hand preference was the long pegboard task. Such a finding is consistent with the view that the long pegboard provides a behavioral measure of hand preference, while the pegs and dots tasks are more closely linked to specific skills. In addition, the correlations between individual preference items and the dichotic right-ear advantage suggest that language lateralization is related to rather different handedness measures than those usually used to define handedness. This finding would suggest that handedness and language lateralization are determined by somewhat different mechanisms.

Different dimensions of hand preference that relate to skilled and unskilled activities.

Hand preference is multidimensional with two major factors and a variable number of minor factors. In the present factor analyses of hand preference, there was no evidence to support Healey, Liederman and Geschwind's (1986) suggestion that hand preference dimensions can be distinguished on the basis of those requiring movement of the distal musculature (fingers and hand) and those requiring movement of the proximal. The first factor reported here relates to "skilled" activities. Hand preference for the use of tools and manipulation of other objects is strongly lateralized in self-professed right- and left-handers. "Less skilled" activities such as picking up objects load on a second and a third factor. Preference for picking up objects including very small ones and relatively heavy ones is much less lateralized, although there appears to be a distinction between activities that involve strength and those that do not. A fourth factor relates to the use of bats and axes, a bimanual activity.

Handedness is not related to self-reported disease incidence.

A hand preference inventory and a disease questionnaire were administered to a sample of 743 undergraduate students. The incidence of left-handedness was not related to the report of any of the diseases surveyed. Among right-handers, preference scores were slightly lower (less right-handed) in those reporting drug allergies or migraine. These data provide no support for the argument that handedness and immune disorders are related.

The effects of time and distance on accuracy of target-directed locomotion: does an accurate short-term memory for spatial location exist?

The present study was an attempt to replicate the findings of an influential set of experiments by Thomson (1980, 1983) in which he demonstrated a highly accurate but transitory short-term memory for target location during locomotion. No evidence of Thomson's rapidly decaying 8 s short-term memory was found in either of the two experiments presented here. The distance to the target, not the elapsed time, was found to be the major variable affecting the accuracy of walks made without the benefit of visual feedback; as target distance increased so did locomotor error. Increasing the elapsed time to more than 8 s between viewing the target and reaching the vicinity of the target had no effect on the accuracy of walks made with eyes closed. When the elapsed time was greater than 30 s, however, performance began to deteriorate. These results suggest, in sharp contrast to Thomson's experiments, that short-term memory for target location decays rather slowly during locomotion. In this regard, short-term memory in locomotor tasks appears to be little different from the kinds of short-term memory associated with other motor acts.

The relation between hand preference and hand performance: what you get depends on what you measure.

In the present investigation, we addressed the relation between manual preference and performance. A total of 52 right-handers and 48 left-handers were tested for manual proficiency and preferences using a range of tasks. Self-professed right-and left-handers showed greater preference for, and superior performance with, the preferred hand. Left-handers use their nonpreferred hand more often and in some instances are more skilled with it than right-handers. There was a subgroup of persons with mixed handedness, who identified themselves as left-handed, wrote with the left hand, and were more skilled with the left hand on dot-filling, but who were otherwise right-handed. Overall, the data indicated that a complete description of handedness will only be provided by careful consideration of the nature of the preference and performance measures one uses.

Neuropsychological test performance of specific diagnostic groups in the Canadian Study of Health and Aging (CSHA).

An overview of specific neuropsychological data from the Canadian Study of Health and Aging is presented. Variables of interest were diagnosis (no cognitive impairment, cognitive loss without dementia, and dementia), language of test administration (French or English), and residence (community or institution). Persons with dementia scored below persons without dementia on all neuropsychological measures except the naming of coloured tokens. Some test differences were small and not clinically meaningful while others were substantial. In particular, and as expected, memory function differed between the groups. Language of test administration and place of residence also influenced neuropsychological results independently of diagnosis. Scores differed on some tests (primarily, visuospatial) depending on whether participants lived in institutions or in the community. Persons tested in French scored below those tested in English on many language-based tests.

An examination of the hypothesis that left-handers die earlier: the Canadian Study of Health and Aging.

The present paper is a prospective examination, using data from the Canadian Study of Health and Aging (CSHA-1 and CSHA-2), of the hypothesis that self-reported left-handers die earlier than right-handers. Persons over age 65 receiving a clinical evaluation in 1991 (n = 2786) as part of CSHA-1 were recontacted in 19956. At baseline, the sample showed a trend for the expected cross-generational decline in nonright-handedness with increasing age (3.2% of those aged 6574 reported being left-handers while 2.1% were left-handers in the 85+ age group). At follow-up, there were no significant differences in mortality between self-reported right-handers (52.6% died), left-handers (56.8%), and ambidexters (46.6%). The Odds Ratio was 1.18 (95% confidence interval 0.721.93) for left- compared to right-handers. There was no evidence that being left-handed increased the risk of death in this sample of elderly Canadians.

Reliability of hand preference items and factors.

The present study examined the test-retest reliability of a 32-item version of the Waterloo Handedness Questionnaire (Steenhuis & Bryden, 1987, 1988, 1989) on 500 subjects. The questionnaire was shown to be reliable in terms of basic factor structure. High test-retest reliability was also found within subjects' responses and across items for both right-handers and left-handers, although left-handers were less consistent than right-handers, particularly with regard to direction of hand preference on individual questionnaire items. Furthermore, the direction of hand preference was more reliable than was the degree of hand preference. These data support a multidimensional view of hand preference in which both direction and degree can be reliably assessed.