Mixed Hand Preference Research Articles

Cerebral laterality as assessed by hand preference measures and developmental stuttering

ABSTRACTThe causes of developmental stuttering, a neurodevelopmental communicative disorder, have not been elucidated to date. Neuroimaging studies suggest that atypical cerebral laterality could be one of such causal factors. Moreover, handedness, a behavioural index for cerebral laterality, has been linked to stuttering and recovery from it. However, findings are conflicting, possibly due to sample selection procedures, which typically rely on self-reported stuttering, and to the fact that handedness is typically assessed with regards to its direction rather than degree. We investigated the possible relationship between handedness and stuttering. This is the first study where children who stutter (CWS) were selected using clinical criteria as well as speech samples and where a non-Western population was studied. Findings from 83 CWS aged 3–9 years (mean = 6.43, SD = 1.84) and 90 age- and sex-matched children who do not stutter (mean = 6.45, SD = 1.71) revealed no differences in their hand preference scores as evaluated by parent-completed Edinburgh Handedness Inventory, for both direction and degree. The severity of stuttering was not found to correlate with the degree of handedness. We suggest that parents and professionals not treat left- or mixed-hand preference as a reason for concern with regards to stuttering.

Season of birth, mixed-handedness, and psychometric schizotypy: Preliminary results from a prospective study

Season of birth and hand preference were examined in a sample of 42 (7 males, 35 females) individuals who were identified as schizotypic based on their scores on selected scales of the Chapman Psychosis Proneness Scales (CPPS) and a matched comparison sample of 42 individuals with non-deviant CPPS scores. Presence or absence of schizotypy was analyzed using chi square tests of independence with the presence or absence of each risk factor serving as the independent variable. Further analyses incorporated independent means t tests to examine mean scores on the CPPS with the presence or absence of each risk factor again serving as the independent variable. Results supported the hypothesis that winter/early-spring birth would be associated with psychometric schizotypy, although the results for mixed-handedness fell just short of statistical significance. However, mixed hand preference was associated with higher scores on MagId and PerAb scales of the CPPS, but not the RSA scale, which suggests that mixed laterality is associated with the more cognitive-perceptual aspects of schizotypy. Results are discussed in relation to previous literature and their relevance to the prediction of schizophrenia-related psychosis.

Going beyond students: An association between mixed-hand preference and schizotypy subscales in a general population

Research on the sub-clinical condition of schizotypy suggests that it is associated with mixed handedness. To date, however, this research has focussed on undergraduate populations. If the association between schizotypy and mixed-handedness is the result of an underlying neurological trait, it is important to demonstrate that the effect extends to the general population. With this in mind, 699 participants were drawn from a wide community sample. Schizotypy was measured using the Psychosis Proneness Questionnaire and handedness was assessed using the Annett inventory. To avoid the sometimes arbitrary definitions of left-, right- and mixed-handed, regression analyses were used to explore the data. There was no evidence of a difference in schizotypy between individuals with a left- or right-hand preference. People with a mixed-hand preference, however, had higher scores on PER–MAG (Perceptual Aberration and Magical Ideation) and HYP–IMP (Hypomania and Impulsive Non-Conformity) scales (positive traits). No effect was observed for the SAN (Social Anhedonia) and PAN (Physical Anhedonia) scales (negative traits). The nature of the association between schizotypy and handedness observed in the current study is similar to that reported for student populations. The possibility that the association is related to response biases or a biological mechanism is discussed.

Mixed-handed persons are more easily persuaded and are more gullible: Interhemispheric interaction and belief updating

Research has shown that persons with mixed hand preference (i.e., who report using their non-dominant hand for at least some manual activities) display an increased tendency to update beliefs in response to information inconsistent with those beliefs. This has been interpreted as reflecting the fact that the left hemisphere maintains our current beliefs while the right hemisphere evaluates and updates those beliefs when appropriate. Belief evaluation is thus dependent on interhemispheric interaction, and mixed-handedness is associated with increased interhemispheric interaction. In Experiment 1 mixed-handers exhibited higher levels of persuasion in a standard attitude-change paradigm, while in Experiment 2 mixed-handers exhibited higher levels of gullibility as measured by the Barnum Effect.

Prenatal Ultrasound Scanning and the Risk of Schizophrenia and Other Psychoses

Prenatal ultrasound exposure has been associated with increased prevalence of left-hand or mixed-hand preference, and has been suggested to affect the normal lateralization of the fetal brain. Atypical lateralization is more common in patients with schizophrenia. We evaluated possible associations of prenatal ultrasound with schizophrenia and other psychoses. We identified a cohort of individuals born in Sweden 1973-1978. During this period, one Swedish hospital (Malmö University Hospital) performed prenatal ultrasound on a routine basis, and all individuals born at that hospital were considered exposed to ultrasound. Children born at hospitals where ultrasound was not used routinely or selectively were considered unexposed. We used Poisson regression analysis to estimate the effect of ultrasound exposure on the incidence of schizophrenia and other psychoses. In all, 370,945 individuals were included in the study, of whom 13,212 were exposed to ultrasound. The exposed group demonstrated a tendency toward a higher risk of schizophrenia (among men, crude incidence rate ratio = 1.58 [95% confidence interval = 0.99-2.51]; among women, 1.26 [0.62-2.55]). However, men and women born in several of the 7 tertiary level hospitals without ultrasound scanning also had higher risks of schizophrenia compared with those born in other hospitals. For other psychoses there were no differences between groups. No clear associations between prenatal ultrasound exposure and schizophrenia or other psychoses were found. Other factors related to place of birth might have influenced the results.

Hand preference in patients with allergy, juvenile cancer, and schizophrenia

Patients with allergy (n = 50), juvenile cancer (n = 50), and schizophrenia (n = 37), and nonpatient controls (n = 200) were asked to indicate their hand preferences on a 7‐point scale (1 = left always, 7 = right always) for the 32‐item Waterloo Handedness Questionnaire. Except for patients with schizophrenia, who exhibited a higher incidence of mixed hand preference, groups showed a clear rightward bias. Further analyses suggested that mixed hand preference in schizophrenia was evident more often for unskilled than skilled hand activities.

Motor difficulties in children with developmental disorders of speech and language.

The motor hand function of 16 children, aged between 4 and 7 years, with developmental speech and language disorders, was compared with that of 16 control children. The children with developmental speech and language disorders were significantly slower than controls on three out of four motor tasks. They were also more likely than controls to have mixed hand preference although this results was not significant. Children with developmental speech and language disorders should be assessed to ensure that motor deficits are diagnosed and that appropriate support is given.

Handedness and visual motion sensitivity in adult dyslexixs

Hand preference and sensitivity to coherent motion in random dot patterns were assessed in a large group of adult dyslexics and controls. The aims were to investigate further the hypotheses that dyslexia is associated with (a) anomalous lateralisation, and (b) an impairment of magnocellular visual processing; and in addition, to investigate a possible relationship between anomalous lateralisation and magnocellular function. Results showed that dyslexia was strongly associated with mixed hand preference, indicative of reduced cerebral lateralisation. Dyslexics also showed reduced visual motion sensitivity, consistent with an impairment of magnocellular visual function. However, independent of dyslexia, nonright-handedness was also associated with poor motion sensitivity, suggesting that there may be a more general relationship between impaired magnocellular function and reduced cerebral lateralisation.

The automated picture-to-word, word-search and motor-identification test in fluent readers

Season of birth and hand preference were examined in a sample of 42 (7 males, 35 females) individuals who were identified as schizotypic based on their scores on selected scales of the Chapman Psychosis Proneness Scales (CPPS) and a matched comparison sample of 42 individuals with non-deviant CPPS scores. Presence or absence of schizotypy was analyzed using chi square tests of independence with the presence or absence of each risk factor serving as the independent variable. Further analyses incorporated independent means t tests to examine mean scores on the CPPS with the presence or absence of each risk factor again serving as the independent variable. Results supported the hypothesis that winter/early-spring birth would be associated with psychometric schizotypy, although the results for mixed-handedness fell just short of statistical significance. However, mixed hand preference was associated with higher scores on MagId and PerAb scales of the CPPS, but not the RSA scale, which suggests that mixed laterality is associated with the more cognitive-perceptual aspects of schizotypy. Results are discussed in relation to previous literature and their relevance to the prediction of schizophrenia-related psychosis.

Observations on the handedness preferences of patients with personality disorders.

A new series of patients with personality disorders has provided an opportunity to extend to both sexes an earlier finding that personality disordered women tend to be mixed handed. Eighty-one subjects completed Annett's handedness questionnaire. The frequency of mixed hand preference in both sexes was similar to that found in the previous study, though deviations from consistent preference were small and dependent on the method used to classify handedness. The hysterical, antisocial and explosive personality types were particularly likely to have mixed handedness. These associations were reflected in small but significant trends among several psychometric variables.

Pitch memory: an advantage for the left-handed.

In an auditory or musical task, subjects made pitch recognition judgments when the tones to be compared were separated by a sequence of interpolated tones. The left-handed subjects performed significantly better than the right-handed and also had a significantly higher variance. Further analysis showed that the superior performance was attributable largely to the left-handed subjects with mixed hand preference.

Ear asymmetry in reaction time tasks as a function of handedness

Reaction times of left-handed subjects to nonverbal auditory stimulation in choice and “go-no go” reaction time tasks were significantly faster when the stimuli were presented to the left ear. Analysis of inter-ear difference scores revealed that the subjects who showed reversed ear preference, i.e. faster reaction times to right ear stimulation, had significantly smaller inter-ear differences and a greater tendency toward mixed hand preference than those who exhibited left ear preference. Additionally, left handers were found to have stimulus-response compatibility effects similar to those previously obtained in right-handed subjects.

Lateral Dominance and Reading Achievement in the Second Grade

them will tend to approach a word from the wrong direction. Monroe (1932) suggested that in moving the eyes to the right, as is required in reading, the left field of vision is obstructed by the bridge of the nose, and consequently the development of left-to-right eye movements may be more difficult for the left-eyed child. She also suggested that a child who has opposite eye-hand dominance may prefer different directional movements for eye and hand, and therefore find the complex hand-eye coordinations necessary in space perception difficult. Harris (1957) found mixed hand preference much more common in a clinical group of disabled readers than in the general school population. He suggested that this lack of consistent hand preference may be the result of a special maturational difficulty or slowness. Balow (1963), working with 302 first-grade children, studied the effect on three measures of reading achievement of these various types and degrees of hand and eye dominance, singly and in interaction: strong, moderate, and mixed hand dominance; normal, crossed, and mixed dominance; and directional confusion. He reasoned that if these characteristics are associated with reading disability, they are also associated with reading achievement in the first grade. Yet, he found no combination of hand dominance and eye dominance, hand-eye dominance and knowledge of right and left, or strength of dominance and knowledge of right and left significantly associated with reading achievement. The problem considered in this study is whether the dominance anomalies specified by Dearborn, Harris, and Monroe are significantly associated with reading achievement in the second grade.