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All sex differences in cognitive ability may be explained by an X-Y homologous gene determining degrees of cerebral asymmetry. Behav Brain Sci 2010. [DOI: 10.1017/s0140525x00042436] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
AbstractMale superiority in mathematical ability (along with female superiority in verbal fluency) may reflect the operation of an X-Y homologous gene (the right-shift-factor) influencing the relative rates of development of the cerebral hemispheres. Alleles at the locus on the Y chromosome will be selected at a later mean age than alleles on the X, and only by females.
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2
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Abstract
AbstractGeary is highly selective in his use of the literature on gender differences. His assumption of consistent female inferiority in mathematics is not necessarily supported by the facts.
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Abstract
AbstractAlthough Geary's partitioning of mathematical abilities into those that are biologically primary and secondary is an advance over most sociobiological theories of cognitive sex differences, it remains untestable and ignores the spatial nature of women's traditional work. An alternative model based on underlying cognitive processes offers other advantages.
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4
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Abstract
AbstractThis commentary focuses on one of the many issues raised in Geary's target article: the importance of gender differences in spatial ability to gender differences in mathematics. I argue that the evidence for the central role of spatial ability in mathematical ability, or in gender differences in it, is tenuous at best.
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5
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Abstract
AbstractSpatial visualization as a key variable in sex-related differences in mathematical problem solving and spatial aspects of geometry is traced to the 1960s. More recent relevant data are presented. The variability debate is traced to the latter part of the nineteenth century and an explanation for it is suggested. An idea is presented for further research to clarify sex-related brain laterality differences in solving spatial problems.
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6
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Abstract
AbstractThe principles of sexual selection were used as an organizing framework for interpreting cross-national patterns of sex differences in mathematical abilities. Cross-national studies suggest that there are no sex differences in biologically primary mathematical abilities, that is, for those mathematical abilities that are found in all cultures as well as in nonhuman primates, and show moderate heritability estimates. Sex differences in several biologically secondary mathematical domains (i.e., those that emerge primarily in school) are found throughout the industrialized world. In particular, males consistently outperform females in the solving of mathematical word problems and geometry. Sexual selection and any associated proximate mechanisms (e.g., sex hormones) influence these sex differences in mathematical performance indirectly. First, sexual selection resulted in greater elaboration in males than in females of the neurocognitive systems that support navigation in three-dimensional space. Knowledge implicit in these systems reflects an understanding of basic Euclidean geometry, and may thus be one source of the male advantage in geometry. Males also use more readily than females these spatial systems in problem-solving situations, which provides them with an advantage in solving word problems and geometry. In addition, sex differences in social styles and interests, which also appear to be related in part to sexual selection, result in sex differences in engagement iii mathematics-related activities, thus further increasing the male advantage in certain mathematical domains. A model that integrates these biological influences with sociocultural influences on the sex differences in mathematical performance is presented in this article.
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7
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Abstract
To investigate the effects of nitric oxide (NO) on passive avoidance learning, L-NAME, D-NAME, and L-arginine were administered i.p. 30 min prior to learning trial; the effects of these substances were tested 24 h later using a passive avoidance apparatus in rats. To reveal the effect of NO on consolidation of acquired memory, L-NAME, D-NAME, and L-arginine were administered i.p. immediately after learning trials and animals were tested 24 h later. Effect of NO on retention was also investigated by injecting L-NAME, D-NAME, and L-arginine (same dosages) 30 min prior to 24 h testing (retrieval). L-NAME administered 30 min before and 24 h after learning trial significantly decreased the avoidance latency but there was no significant effect on consolidation. L-Arginine appeared to enhance the retention of acquired memory significantly, whereas D-NAME had no effect on any testing regime. The results suggest that NO may be involved in learning and retention of passive avoidance.
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Affiliation(s)
- Mehmet Yildirim
- Ondokuz Mayis University, Medical School, Department of Physiology, Samsun, Turkey.
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8
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Rostad K, Mayer A, Fung TS, Brown LN. Sex-related differences in the correlations for tactile temporal thresholds, interhemispheric transfer times, and nonverbal intelligence. PERSONALITY AND INDIVIDUAL DIFFERENCES 2007. [DOI: 10.1016/j.paid.2007.05.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Budak F, Filiz TM, Topsever P, Tan U. CORRELATIONS BETWEEN NONVERBAL INTELLIGENCE AND NERVE CONDUCTION VELOCITIES IN RIGHT-HANDED MALE AND FEMALE SUBJECTS. Int J Neurosci 2005; 115:613-23. [PMID: 15823928 DOI: 10.1080/00207450590523927] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
A neurological theory of intelligence suggesting a direct correlation between nerve conduction velocity and psychometric intelligence was tested. Cattell's Culture Fair Intelligence Test was used to asses the nonverbal intelligence (IQ) of subjects. The motor median nerve conduction velocity from right hand of males was positively correlated with IQ. In subjects with no familial sinistrality (FS-), the motor ulnar-nerve conduction velocity from the right and left hands of males negatively correlated with IQ; there were inverse correlations between IQ and nerve conduction velocity (motor median nerve from right, sensory median nerve from right and left) in females. In subjects with familial sinistrality (FS+), IQ directly correlated with nerve conduction velocity from motor median (right and left), sensory median (right), and motor ulnar (right) nerves, but only in males. The speed hypothesis and neurological theory of intelligence were not supported by these results, which, in contrast, emphasized the importance of sex and familial sinistrality in any theory of intelligence.
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Affiliation(s)
- Faik Budak
- Kocaeli University, Medical School, Department of Neurology, Edirne, Turkey
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10
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Küçükatay V, Balkan S, Yaraş N, Yargiçoğlu P, Ağar A. The effect of pergolide on cognitive performance of young and middle-aged rats. Int J Neurosci 2002; 112:1027-36. [PMID: 12487092 DOI: 10.1080/00207450290026021] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
In this study, we investigated the effect of pergolide, a dopaminergic agonist, on cognitive ability in young and middle-aged rats using the Morris Water Maze (MWM). Pergolide 0.5/mg/day i.p. was administered to young and middle-aged rats, whereas only vehicle was given to their age-matched controls. During the acquisition period of 6 days, young rats showed normal escape latency pattern, which was not affected by pergolide. Middle-aged rats, however, showed poor escape latency pattern, and this poor pattern was also not affected by pergolide. On the 7th day, pergolide decreased retention time of young rats compared to control values. Middle-aged rats also showed reduced retention time. In contrast to the findings of young rats, retention time was not affected by pergolide in middle-aged rats. We concluded that pergolide does not alter escape latency at any age. It has a negative effect on retention time of young rats, whereas it has no effect on middle-aged ones.
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Affiliation(s)
- Vural Küçükatay
- Faculty of Medicine, Department of Physiology, Arapsuyu, 07070 Antalya, Turkey.
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11
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On the biology and politics of cognitive sex differences. Behav Brain Sci 1996. [DOI: 10.1017/s0140525x00042667] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
AbstractThe male advantage in certain mathematical domains contributes to the difference in the numbers of males and females that enter math-intensive occupations, which in turn contributes to the sex difference in earnings. Understanding the nature and development of the sex difference in mathematical abilities is accordingly of social as well as scientific concern. A more complete understanding of the biological contributions to these differences can guide research on educational techniques that might someday produce more equal educational outcomes in mathematics and other academic domains.
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12
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Brain differences, anthropological stories, and educational implications. Behav Brain Sci 1996. [DOI: 10.1017/s0140525x00042539] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
AbstractGeary's anthropological assumptions are questioned as he uses literature influenced by sociobiology to back the claim that Female humans do not engage in environmental orientation. Yet, female gatherers or migrators do need and use spatial skills. Geary's exploration of gender differences in math skills is speculation that hasharmful, ungrounded, and misleading educational implications and applications, particularly in light of research on the status of gender equity in education.
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The twain shall meet: Uniting the analysis of sex differences and within-sex variation. Behav Brain Sci 1996. [DOI: 10.1017/s0140525x0004259x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
AbstractSpatial and mathematical abilities may be “sex-limited” traits. A sex-limited trait has the same determinants of variation within the sexes, but the genetic or environmental effects would be differentially expressed in males and females. New advances in structural equation modeling allow means and variation to be estimated simultaneously. When these statistical methods are combined with a genetically informative research design, it should be possible to demonstrate that the genes influencing spatial and mathematical abilities are sex-limited in their expression. This approach would give an empirical confirmation of Geary's evolutionary speculations.
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14
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Sex differences and evolutionary by-products. Behav Brain Sci 1996. [DOI: 10.1017/s0140525x00042643] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
AbstractFrom the perspective of evolutionary theory, we believe it makes more sense to view the sex differences in spatial cognition as being an evolutionary by-product of selection for optimal rates of fetal development. Geary does not convince us that his proposed selective factors operated with “sufficient precision, economy, and efficiency.” Moreover, the archaeological evidence does not support his proposed evolutionary scenario.
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15
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Between-sex differences are often averaging artifacts. Behav Brain Sci 1996. [DOI: 10.1017/s0140525x00042631] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
AbstractThe central problem in Geary's theory is how differences are conceptualized. Recent research has shown that between-sex differences on certain tasks are a consequence of averaging within sex differences. A mixture distribution models between-sex differences on several tasks well and does not appear congenial to a sexual-selection perspective.
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Able youths and achievement tests. Behav Brain Sci 1996. [DOI: 10.1017/s0140525x00042618] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
AbstractAchievement test differences between boys and girls and between young men and young women, mostly favoring males, extend far beyond mathematics. Such pervasive differences, illustrated here, may require an explanatory theory broader than Geary's.
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Differences in male and female cognitive abilities: Sexual selection or division of labor? Behav Brain Sci 1996. [DOI: 10.1017/s0140525x00042503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
AbstractIn Darwinian terminology, “sexual selection” refers to purely reproductive competition and is conceptually distinct from natural selection as it affects reproduction generally. As natural selection may favor the evolution of sexual dimorphism by virtue of the division of labor between males and females, this possibility needs to be taken very seriously.
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Abstract
AbstractGeary's project faces the severe methodological difficulty of tracing the biological effects of gender on mathematical ability in a system that is massively open. Two methodological stratagems he uses are considered. The first is that pancultural sex differences are biological in nature, which is dubious in the domain of mathematics, since it is completely culture-bound. The second is that sociosexual differences are partly caused by biosexual differences, which renders his thesis unfalsifiable and empirically empty.
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Sex differences in mathematical abllity: Genes, environment, and evolution. Behav Brain Sci 1996. [DOI: 10.1017/s0140525x00042515] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
AbstractGeary proposes a sociobiological hypothesis of how (and why) sex differences in math and spatial skills might have jointly arisen. His distinction between primary and secondary math skills is noteworthy, and in some ways analogous to the closed versus open systems postulated to exist for language. In this commentary issues concerning how genes might affect complex cognitive skills, the interpretation of heritability estimates, and prior research abilites are discussed.
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Abstract
AbstractWe challenge the notion that differences in spatial ability are the best or only explanation for observed sex differences in mathematical word problems. We suggest two ideas from the study of autism: sex differences in theory of mind and in central coherence.
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Is there a comparative psychology of implicit mathematical knowledge? Behav Brain Sci 1996. [DOI: 10.1017/s0140525x00042448] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
AbstractGeary suggests that implicit mathematical principles exist across human cultures and transcend sex differences. Is such knowledge present in animals as well, and is it sufficient to account for performance in all species, including our own? I attempt to trace the implications of Gearys target article for comparative psychology, questioning the exclusion of “subitizing” in describing human mathematical performance, and asking whether human researchers function as cultural agents with animals, elevating their implicit knowledge to secondary domains of numerical performance.
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22
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On an evolutionary model of sex differences in mathematics: Do the data support the theory? Behav Brain Sci 1996. [DOI: 10.1017/s0140525x00042473] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
AbstractThe target article draws on evolutionary theory to formulate a biosocial model of sex differences in quantitative abilities. Unfortunately, the data do not support some of the crucial hypotheses. The male advantage in geometry is not appreciably greater than the male advantagi in algebra, and the greater male variability in mathematics cited by Gear is not cross-culturally invariant.
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Nagels G, Mariön P, Pickut BA, Timmermans L, De Deyn PP. Actigraphic evaluation of handedness. ELECTROENCEPHALOGRAPHY AND CLINICAL NEUROPHYSIOLOGY 1996; 101:226-32. [PMID: 8647035 DOI: 10.1016/0924-980x(96)95566-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The utility of an objective evaluation of motor activity, actigraphy, was examined in the evaluation of handedness. Hand preference was assessed in a homogeneous group of 190 young volunteers using the Edinburgh Inventory (EI). The EI distribution obtained in the population studied was comparable with distributions cited in the literature. Simultaneous actigraphic recordings from both wrists were made in 58 of these subjects for 20 h, starting at 1000 h, using an epoch length of 4 s. Care was taken to include comparable numbers of right- and left-handers (based on EI score) in this subgroup. Two actigraphic parameters were defined. One of these, the Activity Index (AI[x]), is a measure of the difference in total motor activity between right and left wrist. The other, Movement Index (MIy[x]) is a measure of the difference in movement pattern. AI[x] showed a moderate but significant correlation with EI (r = 0.36, P < 0.005). The correlation between MIy[x] and EI was high (r = 0.65, P < 0.0001). Rebinning of the data into 60 s epochs decreased the degree of linear correlation between MIy[x] and EI. We conclude, in contrast to a previous study, that actigraphy can be used to discriminate between dominant and non-dominant hands; that the difference in movement pattern between right and left hand is larger than the difference in total motor activity; and that epoch lengths shorter than the conventional 60 s are more sensitive for this kind of discrimination.
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Affiliation(s)
- G Nagels
- Department of Neurology, Middelheim General Hospital, Antwerp, Belgium
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24
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We are far from understanding sex-related differences in spatial-mathematical abilities despite the theory of sexual selection. Behav Brain Sci 1996. [DOI: 10.1017/s0140525x0004262x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
AbstractI have provided evidence that Geary's model does not explain male dominance in spatial abilities by sexual selection. The current literature concerning the relations of nonverbal IQ to testosterone, hand preference, and right- and left-hand skill, as well as the organizing effects of testosterone on cerebral lateralization during the perinatal period, does not support Geary's arguments.
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25
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Do gender differences in spatial skills mediate gender differences in mathematics among high-ability students? Behav Brain Sci 1996. [DOI: 10.1017/s0140525x00042412] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
AbstractBased on Geary's theory, intelligence may determine which males utilize innate spatial knowledge to inform their mathematical solutions. This may explain why math gender differences occur mainly with higher abilities. In support, we found that mental rotation ability served as a mediator of gender differences on the math Scholastic Assessment Test for two high-ability samples. Our research suggests, however, that environment and biology interact to influence mental rotation abilities.
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26
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Genetic influences on sex differences in outstanding mathematical reasoning ability. Behav Brain Sci 1996. [DOI: 10.1017/s0140525x00042655] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
AbstractSexual selection provides an adequate partial explanation for the difference in means between the distributions, but fails to explain the difference in variance, that is, the overrepresentation of both boys with outstanding mathematical reasoning ability (OMRA) and boys with mental retardation. Other genetic factors are probably at work. While spatial ability is correlated with OMRA, so are other cognitive abilities. OMRA is not reducible to spatial ability; hence selection for navigational skill is unlikely to be the only mechanism by which males have gained an advantage in OMRA.
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27
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Sexual-selection accounts of human characteristics: Just So Stories or scientific hypotheses? Behav Brain Sci 1996. [DOI: 10.1017/s0140525x00042576] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
AbstractWe evaluate three of Geary's claims, finding that (1) there is little evidence for sex differences in object- vs. person-orientation; (2) sex differences in competition, even if biologically caused, lead to sex differences in mathematics only given a certain style of teaching; and (3) sex differences in mental rotation, though real, are not well explained in a sociobiological framework or by the proximate biological variables assumed by Geary.
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A critic with a different perspective. Behav Brain Sci 1996. [DOI: 10.1017/s0140525x00042540] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
AbstractTo the extent that Geary's theory concerning biologically primary and secondary behaviors depends on factor analytic methods and findings, it is woefully weak. Factors have been mistakenly called primary mental abilities, but the adjective “primary” represents reification of a mathematical dimension defined by correlations. Fleshing out a factor beyond its mathematical properties requires much additional quantitative experimental and correlational research that goes far beyond mere factoring.
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Abstract
AbstractAnalyses of bodies of data usually omit some relevant studies. Geary omits (1) some studies looking at functional correlates of basic biological data, (2) studies of developmental implications for functioning, and (3) the recent achievement of acceleration of cognitive development.
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30
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Resources dimorphism sexual selection and mathematics achievement. Behav Brain Sci 1996. [DOI: 10.1017/s0140525x00042564] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
AbstractGeary's model is a worthy effort, but ambiguous on important issues. It ignores differential resource allocation, although this follows directly from sexual selection via differential parental investment. Dimorphism in primary traits is arbitrarily attributed to sexual selection via intramale competition, rather than direct evolutionary pressures. Dubious predictions are made about the consequences of raising mathematics achievement.
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31
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The logic of the sociobiological model Geary-style. Behav Brain Sci 1996. [DOI: 10.1017/s0140525x00042588] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
AbstractGeary's is the traditional view of the sexes. Yet each part of his argument – the move from sex differences in spatial ability and social preferences to a sex difference in mathematical ability, the claim that the former are biologically primary, and the sociobiological explanation of these differences – requires considerable further work. The notion of a biologically secondary ability is itself problematic.
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32
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Some problematic links between hunting and geometry. Behav Brain Sci 1996. [DOI: 10.1017/s0140525x00042552] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
AbstractGeary's emphasis on hunting ignores the possible importance of other human activities, such as scavenging and gathering, in the evolution of spatial abilities. In addition, there is little evidence that links spatial abilities and math skills. Furthermore, such links have little practical importance given the small size of most differences and girls' superior performance in mathematics classrooms.
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33
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Tan U. Correlations between nonverbal intelligence and peripheral nerve conduction velocity in right-handed subjects: sex-related differences. Int J Psychophysiol 1996; 22:123-8. [PMID: 8799775 DOI: 10.1016/0167-8760(96)00006-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The speed hypothesis of intelligence was tested in relation to median nerve conduction velocity (NCV) in right-handed subjects. In total, NCV did not significantly correlate with IQ (Cattell's Culture Fair Intelligence test). The motor and sensory median NCVs correlated with IQ positively linearly in men and negatively linearly in women. These results supported the general, unqualified speed hypothesis of intelligence only for men. It was concluded that the conduction speed of the input-output channels of brain as an information processing unit may differentially contribute to nonverbal intelligence, depending upon sex. The male hormone, testosterone, was suggested to be the main factor responsible for sex-related differences in the IQ-NCV relationships.
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Affiliation(s)
- U Tan
- Department of Physiology, Medical Faculty, Atatürk University, Erzurum, Turkey.
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Tan U, Akgün A, Telatar M. Relationships among nonverbal intelligence, hand speed, and serum testosterone level in left-handed male subjects. Int J Neurosci 1993; 71:21-8. [PMID: 8407147 DOI: 10.3109/00207459309000588] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The relationships among nonverbal intelligence, hand speed, and serum testosterone level were studied in male left-handers ranging in age from 17 to 19 years. Hand speed was measured by a peg moving task. To assess the differences between nonverbal IQs. Cattell's Culture Fair Intelligence Test was used. There was a direct correlation between IQ and testosterone. IQ increased linearly with right-hand speed, which was directly related to testosterone. There was no significant correlation between IQ and left-hand speed, which was not significantly correlated with testosterone. IQ decreased with left- minus right-hand speed, which also decreased with testosterone. It was suggested that nonverbal spatial reasoning ability may be directly associated with the efficiency of left brain, which is favored by testosterone in male left-handers. It was also concluded that the left to right asymmetry in hand speed may depend on efficiency of the right brain in left-handed males.
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Affiliation(s)
- U Tan
- Atatürk University, Medical Faculty, Department of Physiology, Erzurum, Turkey
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35
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Tan U. The relation of body height to handedness in male and female right- and left-handed human subjects. Int J Neurosci 1992; 63:217-20. [PMID: 1304556 DOI: 10.3109/00207459208987197] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The association between body size and the degree of hand preference was studied in male and female right- and left-handed human subjects. Hand preference was assessed by the Edinburgh Handedness Inventory. In left-handers (total sample), there was a significant, negative linear correlation between the degree of left-hand preference and body height. There was no significant correlation between these parameters if the males and females were considered separately. In right-handers (total sample), body height was found to be significantly and negatively linearly correlated with the degree of right-hand preference. A similar correlation was observed in males without familial sinistrality (FS-) and in FS+ females. There was no significant correlation between these parameters in FS+ right-handed males and FS- right-handed females. It was suggested that hormones affecting body height and brain size such as human growth hormone and testosterone would also contribute to the development of cerebral lateralization.
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Affiliation(s)
- U Tan
- Atatürk University, Medical Faculty, Department of Physiology, Erzurum, Turkey
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