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PubMed2004

Handedness and spatial ability: differential patterns of relationships.

The purpose of this exploratory study was to add to our understanding of hemispheric specialisation by examining the relationships between functional laterality (as measured by handedness, eyedness, earedness, and footedness) and spatial tests. A total of 55 males and 170 females were tested for laterality preferences and spatial test performance using a range of six spatial tests. There was a statistically significant relationship between each of the laterality measures employed, with handedness and footedness demonstrating the most robust association. Multiple regression analyses highlighted that once potential confounds were statistically controlled (age, sex, and other types of functional laterality), 3-D rotation/visualisation and speeded visual exploration task performance showed small, but significant, relations with a tendency towards left-handedness over right-handedness in total and secondary (two-handed) scale scores. Flexibility of closure performance was associated with a tendency towards left-handedness in the total and one-handed scale scores. Spatial location memory was the lone spatial ability relating with a tendency towards right-handedness. Overall, these findings offer new insights into the interplay of handedness with alternative measures of laterality as well as with spatial abilities.

Adult↗
PubMed2006

Arm folding, hand clasping, and Luria's concept of "latent left-handedness".

Luria (1947/1970) proposed left-top positions in arm folding (AF) and hand clasping (HC) to be signs of "latent left-handedness". However, research since has revealed that (1) left-top positions are canonical for European right-handers and (2) combined AF/HC measures may provide more information about cerebral laterality than either measure considered alone. We tested whether AF and HC or AF/HC combinations predicted diminished right-handedness for 12 handedness items. Results from 509 healthy participants showed that (1) left-top positions in AF and HC were dominant across participants, as was right-handedness, and a right-top position in HC was associated with attenuated right-handedness, (2) right-hand preference was more frequently associated with congruent AF/HC combinations, especially of the LL type (AF: left-top / HC: left-top), and (3) non-right-hand preference was associated with non-congruent, predominantly LR combinations. We conjecture that the LL type combination indicates left hemispheric dominance for motor actions, whereas the LR combination, in which HC as the distally innervated posture deviates from the canonical pattern, indicates attenuated hemispheric asymmetry. Our data support Luria's proposition that a left-top preference in AF points to "latent" left-handedness, but only if associated with a right-top preference in HC. Consistent left-top preference for the combined AF/HC measure appears to predict right-handedness.

Adolescent↗
PubMed1996

Mixed-handedness in patients with functional psychosis.

BACKGROUND: An excess of non-right-handedness has been shown among patients with schizophrenia. However it is not clear whether this finding can be accounted for by an increase in left-handedness, mixed-handedness or both. It is not known whether atypical patterns of hand preferences occur in other functional psychotic illnesses. METHOD: The Annett hand preference questionnaire was administered to patients with schizophrenia (n = 120); affective psychosis (n = 55); schizoaffective psychosis (n = 41), and control subjects (n = 86). Handedness was classified into three categories: right, mixed and left-handedness. RESULTS: The hand preference patterns of patients with functional psychotic illnesses were not significantly different from controls. Patients with schizophrenia showed a non-significant excess of mixed-handedness compared with controls. Patients with schizophrenia and affective psychosis showed a non-significant decrease in left-handedness compared with controls. CONCLUSIONS: Although our results showed a trend in the hypothesised direction, we failed to demonstrate that patients with psychotic illness differed from controls on self-reported hand preference patterns.

Adult↗
PubMedDate not supplied

[Aetiological factors in left-handedness].

Lateralisation associates the extremities and senses of one side of the body, which are connected by afferent and efferent pathways, with the primary motor and sensory areas of the hemisphere on the opposite side. Dominant laterality denotes the appearance of a dominant extremity or sense in the performance of complex psychomotor activities. Laterality is manifested both as right-handedness or left-handedness, which are functionally equivalent and symmetrical in the performance of activities. Right-handedness is significantly more common than left-handedness. Genetic theory is most widely accepted in explaining the onset of lateralisation. According to this theory, the models of brain organisation asymmetry (anatomical, functional, and biochemical) are strongly, genetically determined. However, the inability to clearly demonstrate the association between genetic factors and left-handedness has led researchers to investigate the effects of the environment on left-handedness. Of particular interest are the intrauterine environment and the factors influencing foetal development, of which hormones and ultrasound exposure are the most significant. It has been estimated that an extra five cases of nonright-handed lateralisation can be expected in every 100 males who were exposed to ultrasound in utero compared to those who were not. Socio-cultural pressure on left-handed individuals was much more severe in the past, which is confirmed by scientific findings that left-handedness is present in 13% of individuals in their twenties, while in less than 1% of individuals in their eighties.

Functional Laterality↗
PubMed1979

Choice of handedness measures in studies of hemispheric specialization.

Left-and right-handers have been reported to differ in lateral hemispheric specialization for cognition. We compared different methods of dividing subjects into handedness groups: preference(a 12-item questionnaire), performance(speed, strength, dexterity), and preference plus performance, and determined which method of handedness classification indicated the greatest group differences on EEG and dichotic measures of lateral specialization. All handedness measures were significantly intercorrelated. These handedness measures were significantly correlated with the dichotic test over the whole population but were significantly correlated with EEG asymmetry only in females. Scoring degree of handedness showed significant relationships to lateral specialization which were not seen when subjects were classified into discrete handedness groups. Ambidextrous subjects performed as well as right- or left-handers on unimanual tasks despite a lack of hand preference. The hand used for writing was shown to be too limited to be used as the sole index of handedness in studies related to cognition.

Adult↗
PubMed1986

Handedness concordance and intelligence discrepancies in identical twins.

The purpose of this study was to determine if the discrepancy in measured intelligence between identical twins concordant for handedness differed measureably from the discrepancy between identical twins discordant for handedness. If handed concordant and discordant twins did differ in terms of the between twin discrepancy in measured intelligence, then one could infer that congenital factors had caused dissociation of handedness and measured intelligence within a twin set. This finding would support Nagylaki and Levy's contention that the found discordance rates for handedness in identical twins is a function of "pathogenic" congenital factors disrupting the genetically determined handedness pattern. More generally, this finding would also support Satz's model with respect to pathological shifts in handedness due to brain insult either in utero or perinatally. However, in the current study, eight sets of identical twins were examined and no evidence was found to support these hypotheses. Instead, in one set where there was a marked discrepancy in measured intelligence, handedness could not be determined precisely for the twin with the lower intelligence quotient.

Journal Article↗
PubMed1993

[Left-handedness and diabetes mellitus of autoimmune origin].

A controversial theory postulates that there is an association between left handedness and immune and speech disorders. There are reports of increased frequency of left handedness in type I diabetic patients. The aim of this study was to compare 65 type I diabetics, 65 type II diabetics and 130 normal controls using a 7 item questionnaire for handedness. No differences were found for strong left handedness. However the frequency of strong right handedness decreased significantly from controls to type II diabetics and type I diabetics. Since less intense right handedness is not the same as left handedness, it is concluded that the theory is not supported by the present findings.

Adult↗
PubMedDate not supplied

Association between non-right-handedness and cleft lip with or without cleft palate in a Chinese population.

The etiology of non-syndromic cleft lip with or without cleft palate (CL +/- P) is unclear, although both familial and environmental factors are implicated. Because CL +/- P occurs at approximately the time of brain lateralization and is most often unilateral, developmental asymmetry effects have been postulated in CL +/- P etiology. Handedness is frequently used as an indicator of brain lateralization; therefore, several studies have examined the relationship between cleft laterality and handedness. However, these studies have had conflicting results. The present study investigated handedness in a Chinese sample of 211 non-syndromic CL +/- P surgical probands (ascertained in Shanghai for family studies of CL +/- P), 221 population-based but unmatched controls, and 272 first-degree relatives of the probands. Handedness was assessed by means of laterality quotients (LQ) calculated from questionnaire data. Mean LQ's were compared, as were various arbitrary definitions of handedness based on the LQ, for cases versus controls, males versus females, right-sided versus left-sided clefts, and cleft lip alone versus cleft lip plus cleft palate. CL +/- P cases had a significantly higher proportion of non-right-handedness (NRH) than controls, regardless of the definition of NRH (P values < or = .001). There were no statistically significant differences for any of the other comparisons. Familiarity of NRH was tested by comparing first-degree relatives of cases to controls; first-degree relatives were found to have a significantly higher proportion of NRH than controls, supporting familial effects in NRH. These results support the concept of a common etiology and/or developmental pathway for CL +/- P and handedness.

Case-Control Studies↗
PubMed1991

Handed asymmetry, handedness reversal and mechanisms of cell fate determination in nematode embryos.

Embryos of the nematode Caenorhabditis elegans exhibit left-right asymmetry with an invariant handedness. The embryonic cell lineage is asymmetrical: although the animal is generally bilaterally symmetrical with only a few left-right asymmetries, many of its contralaterally analogous cells arise via different lineages on the two sides of the embryo. Larvae and adults also exhibit left-right asymmetries with a handedness that is normally invariant. The frequency of animals with opposite handedness was increased among the progeny of adults exposed to the mutagen ethyl methanesulphonate and among animals that developed from embryos treated in early cleavage with chitinase to destroy the egg shell. Reversal of embryonic handedness was accomplished directly by micromanipulation at the 6-cell stage, resulting in mirror-image but otherwise normal development into healthy, fertile animals with all the usual left-right asymmetries reversed. This demonstrates that (1) the handedness of cell positions in the 6-cell embryo dictates handedness throughout development; (2) at this stage the pair of anterior blastomeres on the right is equivalent to the pair on the left; and (3) the extensive differences in fates of lineally homologous cells on the two sides of the animal must be dictated by cellular interactions, most of which are likely to occur early in embryogenesis and appear to have been conserved in widely diverged nematode species.

Animals↗
PubMed1988

Brain injury, handedness, and speech lateralization in a series of amobarbital studies.

Data on handedness and speech lateralization in patients selected for amobarbital studies have frequently been extrapolated to the normal population, despite the high frequency of brain injuries which might alter lateralization in these patients. To achieve a better definition of the relationships between brain injury, handedness, and speech lateralization, we reviewed the records of 237 consecutive patients who underwent amobarbital testing. Brain injuries sufficient to cause right hemiparesis were strongly associated with left handedness and atypical (right hemisphere or bilateral) speech representation. Among nonhemiparetic patients, abnormal extratemporal radiological findings were associated with an increased incidence of left handedness and atypical speech lateralization. It was not possible to demonstrate any alteration in handedness or speech representation resulting from abnormalities restricted to the temporal lobes, although such alterations could not be excluded. Handedness and speech lateralization established using amobarbital studies in neurosurgical patients may not be representative of the normal population.

Adolescent↗
PubMed1997

The relation of planum temporale asymmetry and morphology of the corpus callosum to handedness, gender, and dyslexia: a review of the evidence.

Asymmetry of the planum temporale in relation to handedness, gender, and dyslexia is reviewed. The frequency of rightward asymmetry is rather higher than are estimates of the proportion of right hemisphere speech representation in the general population. Conversely, the frequency of leftward asymmetry is lower than the proportion of the population with left hemisphere speech. Neuro-anatomic asymmetry may relate more to handedness than to language lateralization. There are suggestions that neuroanatomic asymmetry is reduced in females compared to males but the data are inconclusive. Reports concerning handedness and gender differences in callosal structure are conflicting but, as with planum asymmetry, any effect of handedness is as likely to relate to degree as to direction of handedness. It has been reported that the plana are more often symmetrical in size or larger on the right side among dyslexics than controls but this has not always been found. However, greater frequency of atypical (a)symmetry of the planum in dyslexia would be consistent with the absence of a factor which, when present, biases the distribution of planum asymmetry toward the left (and handedness towards the right) as hypothesized by Annett (1985). Studies of the size of the corpus callosum in dyslexia have produced conflicting findings.

Adolescent↗
PubMed1991

Handedness in mice: comparison across eleven inbred strains.

Screening for handedness was performed in 11 inbred strains of mice. Direction and degree of handedness were measured for both males and females in each strain. The data show that there are almost as many right- as left-handed subjects and no strain could be classified as right- or left-handed. Females, however, tend to be more strongly lateralized than males. The range of variation for degree of handedness is pronounced between strains. These results thus suggest that degree of handedness would be the relevant variable in a genetic analysis of handedness in mice. They are in agreement with Collins' previous results showing a response to selection for degree, but not for direction, of handedness.

Animals↗
PubMed1986

Handedness patterns in autism suggest subtypes.

The present study reports preliminary data from two unselected samples of carefully diagnosed autistic subjects (children and adults) and an assessment procedure that includes a large sample of items, appropriate for lower-functioning autistic subjects, with multiple presentations within and between sessions 1 week apart. The study seeks to determine (1) whether a raised incidence of non-right-handedness exists in these samples (2) if so, what constructs best represent this shift in the handedness distribution (i.e., phenotype and CNS substrate) and (3) whether these handedness phenotypes are associated with different levels of cognitive functioning. The results reveal a dramatic shift away from right-handedness in both autistic samples, due to a raised incidence of two phenotypes, manifest left-handedness and ambiguous handedness. The ambiguously handed, who were postulated to represent substantial bilateral CNS pathology due to early brain injury, were found to have much lower intellectual scores in one of the study samples.

Adolescent↗
PubMed2003

Left-handedness as a risk factor for fractures.

Left-handedness has been associated with increased fracture risk in a small number of previous studies. This study reports risks for fractures at the proximal humerus, distal forearm, pelvis, foot, and shaft of the tibia/fibula according to handedness in a case-control study conducted from October 1996 to May 2001 among members of Northern California Kaiser Permanente. Handedness was assessed by questionnaire for 2,841 cases and 2,192 controls, and subjects were categorized as left-handed, right-handed, ambidextrous, or forced to switch from the left to the right hand. Compared to right-handedness, left-handedness was most strongly associated with an increased risk for proximal humerus fractures (adjusted odds ratio (OR)=2.00, 95% confidence interval (CI) 1.33 to 3.01) and less definitively with fractures of the distal forearm (adjusted OR=1.28, 95% CI 0.92 to 1.80), foot (adjusted OR=1.17, 95% CI 0.82 to 1.65), and pelvis (adjusted OR=1.40, 95% CI 0.71 to 2.74). Ambidextrous individuals had elevated risks for fractures of the distal forearm (adjusted OR=2.99, 95% CI 1.42 to 6.30), foot (adjusted OR=2.59, 95% CI 1.13 to 5.97), shaft of the tibia/fibula (adjusted OR=3.91, 95% CI 1.01 to 15.17), and proximal humerus (adjusted OR=2.37, 95% CI 0.85 to 6.65) when compared with right-handed individuals. Those individuals forced to use the right hand demonstrated no increased risk for fractures at any site. These results suggest that handedness does influence fracture risk, but the reasons for this increased risk are unclear.

Aged↗
PubMed2003

Verbal laterality and handedness in patients with intracranial arachnoid cysts.

Left-handedness is most often genetic, but may also follow early, localised damage to the developing brain. This so-called "pathological" left-handedness syndrome is often associated with right hemisphere speech dominance. To find out whether verbal laterality or handedness were affected by congenital, intracranial arachnoid cysts, 51 consecutive patients with temporal or frontal arachnoid cysts were tested for handedness and verbal laterality, as measured with the dichotic listening (DL) technique. Handedness was normal in all subgroups of patients. In the preoperative DL test, only 51 % of the patients showed the normal superiority of the right ear (Right Ear Advantage - REA), significantly different from the REA frequency (74 %) in a normal reference group. Patients with a left temporal, or a frontal cyst had significantly lower preoperative REA frequencies than the reference group, whereas patients with a right temporal cyst did not differ from the reference group. Three to six months after decompressive surgery, the REA frequency (73 %) in the cyst patients was no longer different from that of the reference group. This postoperative normalization was seen both in patients with a left temporal or a frontal cyst. It is concluded that arachnoid cysts may suppress cognitive, cortical functions, and that this suppression can be reversed by surgical decompression of the cyst, even in adults. In our opinion, this cognitive "normalization" may in itself be an indication for decompressive surgery. It is further concluded that, although such cysts are congenital, the pressure from the cyst on the adjacent brain is not strong, nor persistent enough to cause a pathological left-handedness.

Arachnoid Cysts↗
PubMed2004

Isolation and evaluation of dextral-specific and dextral-enriched cDNA clones as candidates for the handedness-determining gene in a freshwater gastropod, Lymnaea stagnalis.

The handedness of gastropods is genetically determined. The freshwater gastropod Lymnaea stagnalis is a normally dextral species, but contains minor sinistral populations. The gene responsible for handedness determination in this species is predicted to function maternally and specifically in the dextral-ovipositing snail. In this study, we used differential screening and cDNA subtraction to isolate eight "dextral genes" that are specific to, or enriched in, the dextral-ovipositing strains of L. stagnalis. These genes were promising candidates for the handedness-determining gene. In order to determine whether the true handedness-determining gene was among them, we tested for genetic correlations between the level of expression of each dextral gene and the handedness phenotype, i.e., the chirality of the next generation offspring, by using a collection of backcross F2 progeny of F1 offspring from crosses between dextral and sinistral strains. Although the present study could not identify the handedness-determining molecules, this approach appears to be promising for the isolation of such developmentally important genes.

Amino Acid Sequence↗
PubMed2005

Handedness in pedophilia and hebephilia.

A sample of 404 adult men underwent assessment following illegal or clinically significant sexual behaviors or interests. Patients' assessments included: administration of a modified version of the Edinburgh Handedness Inventory; recording of patients' phallometric (penile) responses to erotic stimuli depicting adults, pubescent children, and prepubescent children of both sexes; and a tabulation of the numbers of patients' victims, ages 0-11, 12-14, 15-16, and 17 and older, of both sexes. In Study 1, patients' right-handedness scores correlated negatively with their phallometric responses to stimuli depicting prepubescent children and positively with stimuli depicting adults, replicating the pattern described in a previous report (Cantor et al., 2004). Unlike the previous study, however, patients' handedness scores did not significantly correlate with their numbers of prepubescent victims. To explore this discrepancy, Study 2 combined the patients from this replication sample with those in the previously reported sample, categorizing them by the sex and age group of greatest erotic interest to them. The odds of non-right-handedness in men offending predominantly against prepubescent children were approximately two-fold higher than that in men offending predominantly against adults and three-fold higher after eliminating those men with intrafamilial (i.e., incest) offenses. Handedness differences between men erotically interested in males versus females were not statistically significant. These results indicate that the rates of non-right-handedness in pedophilia are much larger than previously suggested and are comparable to the rates observed in pervasive developmental disorders, such as autism, suggesting a neurological component to the development of pedophilia and hebephilia.

Adult↗
PubMed1994

Handedness in women with intrauterine exposure to diethylstilbestrol.

Completed forms containing the Edinburgh handedness inventory were received from 77 women exposed to diethylstilbestrol (DES) in utero. Laterality scores (LSs; range: -100 to +100) were calculated for each respondent based on the handedness inventory and were compared with LSs from 514 female controls. The handedness distribution in the DES daughters was significantly shifted away from strong righthandedness compared with the handedness distribution in the controls (chi-square = 22.0, P < 0.0001). Possible explanations for the association between handedness and DES exposure are presented, and aspects of handedness measurement are discussed.

Adult↗