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PubMed1980

A retrospective study of the relationship between birth history and handedness at six years.

Bakan's hypothesis that sinistrality is caused by perinatal insult was investigated by attempting to relate the handedness of 1094 six-year-old children to many aspects of their birth history ascertained from hospital records. Handedness of the children and their families was obtained by questionnaire. A secular increase in the frequency of sinistrality was noted, from 6.2% among grandparents to 17.5% among the children. Most boys were left-handed than girls. Only two aspects of birth history predisposed to sinistrality: boys born by breech delivery and children born to primiparous mothers over 38 years old were more likely to be left-handed.

Child↗
PubMed1993

Handedness in twins with schizophrenia: was Boklage correct?

Boklage's report of increased non-right handedness among monozygotic twins with schizophrenia has been cited as evidence to support an association of abnormal brain lateralization with the development of schizophrenia. The present study found no such association. Two previous attempts to replicate Boklage's findings (Luchins et al. 1980; Lewis et al. 1989) also reported little support. Studies of twin handedness do not appear to support an association of brain lateralization and schizophrenia.

Adolescent↗
PubMed2006

Individual differences in risk perception versus risk taking: handedness and interhemispheric interaction.

Research indicates that right-hemisphere mechanisms are specifically sensitive to and averse to risk. Research also indicates that mixed degree of handedness is associated with increased access to right hemisphere processing. Accordingly, it was predicted that mixed-handers would exhibit greater risk aversion. Participants were presented with various risky activities and were asked to rate (i) the perceived risk, (ii) the perceived benefit, and (iii) their likelihood to engage in each activity. No handedness differences were found for any of these ratings. Regression analyses, however, indicated that the likelihood to engage in risky activities was predicted primarily by the perceived risks in mixed-handers and by the perceived benefits in strong-handers.

Adolescent↗
PubMed2004

Handedness is mainly associated with an asymmetry of corticospinal excitability and not of transcallosal inhibition.

OBJECTIVE: The study aims to compare transcallosal inhibition (TI), as assessed by the paired-pulse transcranial magnetic stimulation (TMS) technique, in a sample of right-handed subjects (RH) and left-handed subjects (LH). Motor thresholds (MTs) and motor evoked potential (MEP) amplitudes were also measured in the two groups, as an index of corticospinal activity. METHODS: Thirty-two normal subjects (16 RH and 16 LH) were recorded with a paired-pulse TMS paradigm (intensity of both pulses=120% of MT). The inter-stimulus intervals (ISIs) were 2, 4, 6, 8, 10, 12, 14, 16, 18, and 20 ms for both motor cortices, and MEP responses were recorded from the abductor digiti minimi muscles. RESULTS: Both groups showed a clear TI centred around the 12 ms ISI, but no difference was found as a function of handedness or of hemisphere. On the other hand, the two groups differed in terms of corticospinal activity, since the hand motor dominant hemisphere had lower MTs than the non-dominant one in LH, and larger MEP amplitudes for the right hand were found in RH. CONCLUSIONS: Results point to a functional asymmetry of the motor cortex on the hand-dominant versus the non-dominant hemisphere, while handedness does not seem associated with functional differences in callosal inhibition, as measured by the inter-hemispheric paired-pulse TMS technique.

Adult↗
PubMed2003

Change of handedness in cholesteric liquid crystalline phase for N-phthaloylchitosan solutions in organic solvents.

The influence of concentration on the helicoidal change of N-phthaloylchitosan (PhCh) solutions in Me2SO, DMAc and DMF was investigated by means of circular dichroism (CD). The critical concentrations to form liquid crystal phase in these three solvents were 43, 45 and 48 wt.%, respectively as measured with polarized optical microscope. There were two kinds of CD peaks, sharp peaks with absorption maximum at about 330 nm induced by the helical conformation of molecular chain, and very broad peaks covering almost whole visible region induced by the cholesteric helix of mesophase. The later only appeared in concentrated solutions with the concentration higher than the critical concentration. The handedness of both levels of helicoidal structures changed from left- to right-handed with the increase of concentration for PhCh/Me2SO solutions. The chirality transfer occurred between these two chiral levels. For PhCh/DMAc and PhCh/DMF systems, only the handedness of helical conformation reversed, but the cholesteric helix did not change. As a method to measure critical concentration, CD is more sensitive than polarized optical microscopy (POM).

Chitin↗
PubMed1997

Factor analyses of handedness items in left and right-handed intellectually gifted and nongifted children.

Handedness questionnaire items from the General Scale of the Lateral Preference Schedule (Dean, 1988) were administered to 423 intellectually gifted and 226 nongifted children to investigate the underlying processes that contribute to laterality. Handedness items were factor analyzed using principal components (PC) analysis with varimax rotation. PC analyses computed separately for gifted and nongifted left and right-handed writers yielded very different factor structures. Left-handers (regardless of gifted status) tended to have factor structures marked by items that loaded saliently on more than one factor. Whereas a four factor solution best fit the data for the nongifted left-handers, a three factor solution was the best fit for the gifted left-handed children. The factor structure for the left-handed gifted children was marked by two factors where the item "draw" was the only item to load both positively and saliently, a pattern not evident among the nongifted left-handers. These results suggested different underlying patterns contributing to laterality among these groups of children.

Child↗
PubMed2006

Hand preference and performance in 20 pairs of monozygotic twins with discordant handedness.

The differences between right (RH) and left (LH) handers reported in the literature on fine motor tasks, has traditionally been interpreted relative to purported functioning of the cerebral hemispheres. However, conclusive evidence for performance differences which are intrinsic to handedness per se is difficult to obtain unless left and right handers are compared who are similar in their genetic and environmental background. The present study therefore, employed a monozygotic (MZ) twin design which minimizes differences in genetic variation between the two groups. Forty female monozygotic twins (20 pairs) were selected on the basis of discordance of writing hand. Their laterality preferences were assessed and they were tested for differences on hand performance tasks (dot filling, finger tapping, and peg moving). The results revealed that on the hand and foot preference inventories, the right-handers were more strongly lateralized than their left-handed sisters, and that the left-handers had greater variation in their laterality scores. There were substantial correlations between preference and performance scores. The analyses not only revealed the obvious strong main effects of writing hand on performance tasks, but interaction effects of handedness on the peg-moving task. The dot filling task differentiated the writing versus non-writing hand considerably better than either of the other two performance tasks. However, no evidence was found to indicate that twins who wrote with their left hands showed poorer performance than their right-handed twin sisters.

Female↗
PubMed1999

Handedness and lexical skills in undergraduates.

The right shift (RS) theory of handedness and cerebral dominance (Annett, 1972, 1985) suggested that individual differences for patterns of cerebral dominance may be associated with different types of risk to cognitive functions. The higher prevalence of dextrality than sinistrality in humans depends on a single gene (RS+) which facilitates left hemisphere specialisation for speech but at the expense of some right hemisphere function (Annett, 1992b; Kilshaw and Annett, 1983). RS-- genotypes have random asymmetries for hand and brain while RS++ genotypes have strong right shift. Three samples of undergraduates were given tests of phonological processing and of real word homophone discrimination. As predicted, phonology was poor in comparison with homophone discrimination toward the left of the laterality continuum while the reverse was true to the right of the continuum. When groups with specific difficulty for each type of test in comparison with the other were distinguished, those with poor phonology were less dextral and those with poor homophone discrimination were more dextral for hand preference than the rest of the sample. Siblings differed for handedness also, consistent with the argument for a genetic influence.

Adolescent↗
PubMed2000

Intermanual coordination in relation to handedness, familial sinistrality and lateral preferences.

Intermanual coordination assessed by alternating finger tapping and finger-tapping asymmetry were investigated in 105 healthy right- and 105 left-handers and related to handedness, familial sinistrality and lateral preferences (in hand-clasping, arm-folding and eyedness). Compared to right-handers, left-handers with less pronounced left-hand preferences (Subgroup B) showed higher values in intermanual coordination and lower values in finger-tapping asymmetry. Moreover, familial sinistrality and eyedness interacted with handedness effects. While in right-handers intermanual coordination was significantly higher in subjects with dominant left eye, in left-handers of the Subgroup B it was somewhat higher in those with dominant right eye. Higher values in intermanual coordination and reduced asymmetry in finger tapping may be associated with a greater bihemispheric control and better performance in fast bimanual movements.

Adult↗
PubMed1991

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.

Adult↗
PubMed1995

Factoring handedness data: I. Item analysis.

Recently in this journal Peters and Murphy challenged the validity of factor analyses done on bimodal handedness data, suggesting instead that right- and left-handers be studied separately. But bimodality may be avoidable if attention is paid to Oldfield's questionnaire format and instructions for the subjects. Two characteristics appear crucial: a two-column LEFT-RIGHT format for the body of the instrument and what we call Oldfield's Admonition: not to indicate strong preference for handedness item, such as write, unless "... the preference is so strong that you would never try to use the other hand unless absolutely forced to...". Attaining unimodality of an item distribution would seem to overcome the objections of Peters and Murphy. In a 1984 survey in Boston we used Oldfield's ten-item questionnaire exactly as published. This produced unimodal item distributions. With reflection of the five-point item scale and a logarithmic transformation, we achieved a degree of normalization for the items. Two surveys elsewhere based on Oldfield's 20-item list but with changes in the questionnaire format and the instructions, yielded markedly different item distributions with peaks at each extreme and sometimes in the middle as well.

Australia↗
PubMed1992

Foot and eye preferences in adults: relationship with handedness, sex and age.

Age, sex, and handedness effects in foot and eye preferences were studied by questionnaire in large samples of normal adult populations from five different countries (total sample, n = 5064). Foot and eye preference were significantly associated with handedness category (right or left) in all the 10 sex by country samples for foot, and in 9/10 samples for eye. The overall frequencies of crossed preferences were 5% between hand and foot and 19.5% between hand and eye. In right-handers, a gradual shift toward the "right" with increasing age was systematically observed, both for footedness and eyedness. The proportion of crossed hand-foot preference was higher in men than women (7.4% vs 2.5%), and higher in left-handers than right-handers (16.3% vs 4.1%). Sex differences in the proportion of crossed hand-eye preference were variable from one country to the other.

Adolescent↗
PubMed1977

On the probability of pathological right-handedness.

The increased incidence of manifest left-handedness in retardates and epileptics has been attributed to a shift in handedness following early brain injury. Predictive models using this hypothesis have presumed an equipotentiality for shifts in hemispheric dominance whether a left or a right hemisphere is the originally dominant, injured hemisphere. This note demonstrates that the presumption of equipotentiality may be relaxed without significant effect upon the conclusions reached using the predictive models.

Brain Damage, Chronic↗
PubMed1978

Handedness and the mental rotation of perceived patterns.

The present experiment investigated the effect of hemispheric dominance, as indicated by handedness, and perceptual processing. Displays containing two visual patterns were presented to right- and left-handed subjects who classified the two patterns as being the same or different. Also the two patterns in a display were in either an identical orientation or nonidentical orientations. Overall, left handers were faster than right handers at the "same-different" judgement. Additionally, latency increased with the angular discrepancy in orientation between patterns for both handedness groups but this increase was smaller for left handers than for right handers. Apparently, left handers evaluate overall perceptual similarity faster than right handers and they also mentally rotate perceived patterns of discrepant orientations faster than right handers. These findings contradict previous generalizations that left handers are deficient perceptually. Moreover, the present results support the position that left handers should be faster at global perceptual tasks because left handers have less neural distance than right handers mediating the transmission of information between the locus of perception and the locus of dominance.

Adult↗
PubMed1979

Multiple birth risk factors and the distribution of handedness.

In this study, we attempted to maximize the likelihood of replicating Bakan's (1971, 1977a) observations that left-handedness was more probable in college students who were the progeny of "high-risk" births. To do this, the relationships between handedness and a combination of factors known to be associated with birth risk were computed. The observed relationships proved to be trivial and thus the validity of Bakan's hypothesis was questionned.

Adult↗
PubMed1980

handedness in engineering and psychology students.

Patterns of handedness were compared in engineering and psychology students using a questionnaire developed by Oldfield (1971). Engineering students are highly selected in terms of mathematico-spatial skills while psychology students are representative of typical undergraduate populations. In general the incidence of right- and left-handedness was according to expectation for the two groups. However, the engineering sample exhibited a significantly greater dextrality then the psychologists. Some implications of this finding were discussed.

Engineering↗
PubMed1980

Lateral eye movement and handedness as measures of functional brain asymmetry in learning disability.

Evidence is presented which suggests that learning disability is related to lateral asymmetry. Significant differences were found in lateral eye movement and handedness between a learning disabled group and a control group of normal learners. Left lateral eye movement and right handedness was the predominant pattern exhibited in learning disability. These results support Day's notion that left lateral eye movement is associated with educational difficulties. They also provide evidence concerning Orton's hypothesis that mixed cerebral dominance characterizes the learning disabled.

Child↗