Evaluating the Empirical Support for the Geschwind-Behan-Galaburda Model of Cerebral Lateralization

The Geschwind-Behan-Galaburda (GBG) model of cerebral lateralization provides a complex but testable theory of the origins and associates of cerebral lateralization. An overall evaluation of the model suggests that it is not well supported by empirical evidence and that in the case of several key theoretical areas, the evidence that does exist is inconsistent with the theory. In particular: the concept of "anomalous dominance" is shown to be theoretically and methodologically flawed; a meta-analysis of the relationship between handedness and immune disorders finds a marginal overall association, and while three conditions (allergies, asthma, and ulcerative colitis) do show significant associations with left-handedness, two other conditions (myasthenia gravis and arthritis) show significant negative associations with left-handedness. Finally, a review of the origins of the neural crest, and its associations, suggests there is almost no empirical support for the GBG theoretical model in this area.     

Reduced lateralization in verbal dichotic listening in adolescent psychopaths

One possible explanation for previous findings of abnormal linguistic processing in psychopaths is that they are less lateralized for verbal processes. This study tests the hypothesis that adolescent psychopaths show evidence of reduced lateralization on a verbal dichotic listening task. Four self-report and behavioral measures of psychopathy were used to define psychopathy using cluster analytic techniques in 40 juvenile offenders aged 13 to 18 years. Psychopaths were found to have reduced ear asymmetries relative to nonpsychopaths, a result indicating reduced lateralization for verbal material. The effect does not appear to be mediated by group differences in age, ethnic background, IQ, overall performance, left-handedness, selective attention to one ear, or interhemispheric transfer deficits. This result suggests that the previous finding by Hare and McPherson is robust, provides some preliminary validity for the assessment of psychopathy before age 18, and indicates initial support for the utility of cluster analytic techniques in the assessment of psychopathy.     

Effects of intertrial interval, orientation, and adaptation on orientation discrimination measured with a yes-no signal detection paradigm

This paper describes a performance measure of lateral dominance, the Target Tests, which provides separate assessments of manual speed and accuracy within a relatively simple paper-and-pencil format. The Target Tests were administered to 111 normal adults, and scores were examined with respect to handedness, familial left-handedness, and sex. The tests significantly differentiated between right- and left-handers. Target scores were substantially correlated with the Harris Tests of Lateral Dominance, suggesting adequate reliability and validity. The means, standard deviations, and ranges for the preferred and nonpreferred hands for both handedness groups were nearly identical. The Target Tests provide a convenient instrument for assessing motoric lateralization of speed and accuracy in clinical and research settings.     

Breast cancer and cerebral laterality

In reviewing and summarizing work at our institution, we have identified some surprising consistencies in patients with breast cancer. Breast cancer shows four features of cerebral laterality: excess left-handedness, atypical season-of-birth patterns, the risk factor of advanced maternal age, and an association with prenatal sex hormones. Since hypopigmentation also relates to cerebral laterality, a consequence of the association of breast cancer and cerebral laterality is that eye color should be measured as a function of side of disease and age at diagnosis in women with breast cancer.     

Sex differences in left-handedness: a meta-analysis of 144 studies

Human handedness, a marker for language lateralization in the brain, continues to attract great research interest. A widely reported but not universal finding is a greater male tendency toward left-handedness. Here the authors present a meta-analysis of k = 144 studies, totaling N = 1,787,629 participants, the results of which demonstrate that the sex difference is both significant and robust. The overall best estimate for the male to female odds ratio was 1.23 (95% confidence interval = 1.19, 1.27). The widespread observation of this sex difference is consistent with it being related to innate characteristics of sexual differentiation, and its observed magnitude places an important constraint on current theories of handedness. In addition, the size of the sex difference was significantly moderated by the way in which handedness was assessed (by writing hand or by other means), the location of testing, and the year of publication of the study, implicating additional influences on its development.     

Handedness on Tristan da Cunha: The Genetic Consequences of Social Isolation

Provins (1990) has suggested that the apparently low incidence of left-handedness on the island of Tristan da Cunha is the result of social pressures such as deference to authority and group conformity, and that “any genetic factor determining left-handedness must be very weak”. Here we use a large number of Monte Carlo simulations (n = 10,825) of the growth of the population of Tristan da Cunha from 1827 to 1961, to show that if the original population was randomly selected from a large population with a typical gene-frequency, then a combination of founder effects, genetic drift and evolutionary bottlenecks can readily explain the fairly low incidence of left-handedness that was found. Indeed in 15% of the simulations the c-allele, which is postulated to be responsible for left-handedness, has disappeared entirely, resulting in a population with no left-handers at all. The data from Tristan da Cunha are therefore entirely compatible with a genetic model of left-handedness.     

LKB1蛋白在食管鳞癌组织中的表达及意义

为了探讨肝激酶B1（LKB1）蛋白在食管鳞癌组织中的表达水平及其与食管鳞癌临床特征及生存期的关系,应用免疫组化方法检测120例食管鳞癌患者组织中LKB1蛋白表达情况并对诸多临床特征进行相关性分析研究,发现LKB1蛋白在食管癌旁正常组织的阳性表达率高于癌组织;LKB1蛋白表达与患者年龄、性别、肿瘤部位、病变长度及浸润深度无关而与分化程度、淋巴结转移及临床分期（TNM）相关,且LKB1蛋白阴性组预后较阳性组差.可见LKB1视为抑癌基因影响食管鳞癌的预后,可能成为食管鳞癌新型的临床预后指标之一.     

Evaluation of empirical methods and methodological foundations of human left-handedness

The methodological and empirical foundations underlying the theories on human left-handedness are examined, including the definition and classification of left-handedness, its relation to pathology, and the results on family, adoption, and twin research. It is argued that major research findings on left-handedness are based on inadequate empirical methods, and the concrete definitions and assessment procedures do not meet validity and reliability criteria. This also casts doubt on the relationship between left-handedness and pathology reported in the literature. Furthermore, findings from family, adoption, and twin studies do not allow interpretation of possible direct genetic contributions to explaining left-handedness. It is concluded that the methodological limitations of a causal explanation should encourage an examination of the epistemological and methodological premises of theory formulation. The functional method and a theoretical framework based on early childhood experiences and the neural plasticity of the brain may be more appropriate for the selection of empirical methods in research of human left-handedness.     

血小板计数升高对肺癌诊断的临床参考价值

为了探讨血小板计数（blood platelet count,BPC）升高对肺癌诊断的临床参考价值,收集335例肺癌患者和157例肺部良性病变患者术前BPC和相应的,临床病理资料,应用SPSS统计软件分析BPC与肺癌临床病理的关系。结果显示,BPC在肺癌患者显著高于肺良性病变者;BPC在肿瘤直径较大（d〉3cm）的肺癌...     

Familial sinistrality, sex, and laterality differences in naming and Lexical Decision Latencies of right-handers

Sixty-four subjects, divided into four groups of 16 according to sex and familial sinistrality (FS), were given a lateralized Object-Naming Latency Task (ONLT) and a Lexical Decision Latency Task (LDLT). Both tasks showed RVF superiorities. On the ONLT a sex × FS × visual field interaction was obtained, with FS− females and FS+ males showing comparably smaller RVF superiorities than FS+ females and FS− males. On the LDLT an FS by Stimulus Type (word-nonword) interaction was found, FS− subjects being more RVF superior for nonword trials and FS+ subjects more RVF superior for word trials. If one compared only FS− males and females, as some studies have done, greater RVF superiorities obtained for males than females on both the ONLT and word trials of the LDLT. However, FS+ subjects showed the opposite pattern. The data support neither the simple model of FS nor sex influence on language laterality. Data aslso suggest that a history of maternal versus paternal left-handedness may affect lateralization differently in the sexes.     

食管鳞癌患者高血小板血症与预后关系分析

探讨食管鳞癌患者高血小板血症与临床病理特征及预后的关系,回顾性分析340例食管鳞癌患者术前血小板计数,结果显示高血小板血症与肿瘤长度、分化程度、肿瘤分期及淋巴转移密切相关（P〈0．05）,而与性别、年龄及肿瘤位置无关（P〉0．05）;高血小板血症者的生存率明显低于血小板计数正常者（P〈0．001）;并且高血小板血症是影响食管鳞癌患者预后的独立因素。因此高血小板血症与食管鳞癌的进展及不良预后有关。     

Pathological left-handedness: Evaluation of a model

This study investigated the relationship between manifest handedness and the localization of EEG abnormalities in a large group of mentally retarded persons. Persons who had abnormal EEG recordings, regardless of whether the dysfunction was bilateral or asymmetric, exhibited approximately twice the incidence of left-handedness than persons who had normal EEG's. Data for persons having asymmetric damage support a model of pathological left-handedness, with left-handers showing a substantially higher probability of having left brain dysfunction than right-handers.     

Why do High IQ Societies Differ in Intellectual Achievement? The Role of Schizophrenia and Left-Handedness in Per Capita Scientific Publications and Nobel Prizes

Previous research has attempted to understand why countries with relatively favorable conditions and high estimated average IQs (such as Finland and Japan) have a relatively low per capita number of scientific Nobel prizes. In the present study, we examine whether there is a relationship between national schizophrenia and left-handedness prevalence, on the one hand, and per capita scientific and literary achievement, on the other hand, in countries with IQ estimates of at least 90. We found that per capita science and literature Nobel prizes and scientific publications are strongly negatively associated with schizophrenia and strongly positively correlated with left-handedness. There also was a very pronounced negative correlation between schizophrenia rate and left-handedness rate. These results suggest that genius can be regarded as a combination of very high IQ, aspects of high-functioning autism (specifically low empathy) plus relatively low impulse control, consistent with observations of intellectually outstanding individuals, and the fact that schizophrenia appears to constitute the opposite pole of these aspects of autism spectrum. We posit differences in androgen levels as a possible underlying explanation for these findings.     

Left-handed wrestlers are more successful

It has been reported that there is a high proportion of left-handers among top athletes in different sports. In this study, the goal was to examine the rate of left-handedness in the top wrestlers at the world championships for achievement by left-handed wrestlers. The rate of left-handedness was higher in wrestlers with medal honors compared to wrestlers without medals for both men and women. The winning numbers and match degrees were higher in the left-handed wrestlers than in both right- and mixed-handed wrestlers among top international wrestlers.     

Sex, handedness, mathematical ability, and biological causation

An important part of Benbow's (1988) assertion that sex differences in mathematical ability are primarily due to biological factors is the link between a trait that is assumed to reflect differences in brain organization (left-handedness) and mathematical giftedness. It is shown that the link between mathematical giftedness and an increased prevalence of left-handedness is not convincing. However, Benbow's (1986) data do show a convincing link between strong right-handedness and the lack of mathematical giftedness, in agreement with Annett and Manning's (1990a, 1990b) recent work.     

Is There a Link between Irritable Bowel Syndrome and Left-Handedness?: An Exploratory Study

Recent research has found that people with Irritable Bowel Syndrome (IBS) and those with Inflammatory Bowel Disease (IBD) show a relative deficit in verbal IQ, compared to their own performance IQ, and the IQ of a healthy comparison group. It has been suggested that the elevated prevalence of left-handedness shown in previous studies investigating people with IBD is due to compromised left-hemisphere development. This may be associated with a decrement in certain cognitive functions such as verbal IQ. A shift in brain dominance from left to right has been found in many atopic and immunological diseases as well as in autonomic dysfunctions. It was uncertain whether this would apply to people with IBS, a functional disorder in which the cause or causes remain unclear. Therefore, the aim of this preliminary study was to investigate whether people with IBS have an increased prevalence of left-handedness. It was found that there was an association between IBS and left-handedness, showing that further research on this association both in IBS and other functional disorders (as well as on the similarities between IBS and IBD) is warranted.     

Is there a link between irritable bowel syndrome and left-handedness?: An exploratory study

Recent research has found that people with Irritable Bowel Syndrome (IBS) and those with Inflammatory Bowel Disease (IBD) show a relative deficit in verbal IQ, compared to their own performance IQ, and the IQ of a healthy comparison group. It has been suggested that the elevated prevalence of left-handedness shown in previous studies investigating people with IBD is due to compromised left-hemisphere development. This may be associated with a decrement in certain cognitive functions such as verbal IQ. A shift in brain dominance from left to right has been found in many atopic and immunological diseases as well as in autonomic dysfunctions. It was uncertain whether this would apply to people with IBS, a functional disorder in which the cause or causes remain unclear. Therefore, the aim of this preliminary study was to investigate whether people with IBS have an increased prevalence of left-handedness. It was found that there was an association between IBS and left-handedness, showing that further research on this association both in IBS and other functional disorders (as well as on the similarities between IBS and IBD) is warranted.     

Maternal cradling bias in baboons: The first environmental factor affecting early infant handedness development?

The most emblematic behavioral manifestation of human brain asymmetries is handedness. While the precise mechanisms behind the development of handedness are still widely debated, empirical evidences highlight that besides genetic factors, environmental factors may play a crucial role. As one of these factors, maternal cradling behavior may play a key role in the emergence of early handedness in the offspring. In the present study we followed 41 Papio anubis infants living in social groups with their mother for which direction (e.g., left- or right-arm) and degree of maternal cradling-side bias were available from a previous published study. We assessed hand preferences for an unimanual grasping task at three developmental stages: (A) 0–4, (B) 4—6, and (C) 9–10 months of age. We found that individual hand preferences for grasping exist as soon as the first months of age, with a population-level left-handedness predominance, being stable until 6 months; to wit the period during which juveniles are mainly carried by their mothers. More importantly, this early postnatal handedness is positively correlated with maternal cradling lateralization. Interestingly, hand preferences assessed later in the development, once juveniles are no longer carried (i.e., from 9 to 10 months of age), are less dependent from the maternal cradling bias and less consistent with the earlier developmental stages, especially in infants initially cradled on the right maternal side. Our findings suggest that the ontogenetic dynamics of the infant's hand preference and its changes might ultimately rely on the degree of infant dependence from the mother across development.     

Left-handedness: a marker for decreased survival fitness

Life span studies have shown that the population percentage of left-handers diminishes steadily, so that they are drastically underrepresented in the oldest age groups. Data are reviewed that indicate that this population trend is due to the reduced longevity of left-handers. Some of the elevated risk for sinistrals is apparently due to environmental factors that elevate their accident susceptibility. Further evidence suggests that left-handedness may be a marker for birth stress related neuropathy, developmental delays and irregularities, and deficiencies in the immune system due to the intrauterine hormonal environment. Some statistical and physiological factors that may cause left-handedness to be selectively associated with earlier mortality are also presented.     

Left-handedness: association with college major, familial sinistrality, allergies, and asthma

366 juniors, seniors, and graduate students from seven departments at The Ohio State University were administered the 10-item Edinburgh Handedness Inventory and asked questions concerning familial handedness and personal incidence of allergies or asthma. The rate of left-handedness was 15.6% among the male students and 12.9% among the females. Maternal handedness was significantly related to female offspring handedness and to the incidence of allergies and asthma in both males and females. Departmental incidence of left-handedness ranged from a low of 7.5% (Microbiology) to a high of 21.7% (Law).