Helmuth Nyborg

Spatial ability in men and women: Review and new theory

Abstract Results from research on spatial abilities are selectively reviewed. Differences are noted in the effect of puberty on spatial ability of men and women, in the development of spatial ability in early- and late-maturing boys and girls, and in the spatial ability of feminine men and masculine women. Abnormalities are described in the spatial ability of men and women with hormonal disturbances. Variations are found in the spatial ability of women during the menstrual cycle. These findings are considered to lack an adequate explanation, so a new theory is proposed to account for them. The theory considers the cerebral level of estrogen to play an essential role in the expressions of spatial ability while testosterone is said to modulate actions of estrogen. The sex specific ontogenetic pattern of plasma hormone values and the loci of their biological action are outlined, and central mechanisms for hormone-brain-behavior relations are discussed. The theory is used to account for recent findings on spatial ability of women and men. Several implications of the theory are considered, and experiments needed to test the theory directly are discussed.

Racial/ethnic variations in male testosterone levels: A probable contributor to group differences in health

Racial and ethnic variations in serum testosterone levels were investigated among a large sample of male Vietnam era veterans. Based on geometric means, significant average differences were found between 3,654 non-Hispanic white and 525 black individuals. The geometric mean for testosterone levels among 200 Hispanic individuals was similar to that of non-Hispanic white individuals. Regarding two other racial/ethnic groups (Asian/Pacific Islanders and Native Americans), no significant differences were found, due perhaps to small sample sizes. Results were interpreted as having considerable potential for explaining some of the race differences in the incidences of cardiovascular diseases, hypertension, and prostate cancer.

Occupation and Income Related to Psychometric "g".

The regressions of occupational status and income on psychometric g factor scores were examined in large samples of White (W) and Black (B) American armed forces veterans in their late 30s and who are fairly representative of the population of employed W and B males. These results indicate that when Bs and Ws are matched on g scores, there is no evidence of discrimination unfavorable to Bs for job status at any level of g. Nor are Bs with the same g scores as Ws disadvantaged in income when they are above the median level of g in the total sample. In fact, on both variables — job status and income — Ws turn out to be the relatively more disadvantaged group when the level of g is taken into account.

Sex Differences in g

Publisher Summary This chapter explores whether males and females differ in general intelligence, g . It argues that both, total summed IQ scores of intelligence in general, and the Principal Component or Principal Factor analytic g scores of general intelligence g might, under certain methodological circumstances, represent a slightly contaminated proxy for the latent variable g . Were that the case, methodological shortcomings would overshadow a potentially small sex difference in g. A six-point scale for evaluating sex difference studies in term of adequacy of methodology was therefore developed and applied to a number of selected studies—some of them reporting a sex difference, some not. Studies earning less than 5 points run, according to the chosen scale cut-off point an unacceptable high risk of committing either a type I or type II error. The literature review indicates that only two contemporary studies earn five or more points, and thus satisfy the quality demand. Both studies used the Schmid–Leiman hierarchical factor analytic approach, both factored in the relevant point-biserial correlations, and both studies found a significant male lead in general intelligence g . Finally, the chapter demonstrates that a simple tape measure of head circumference correlates significantly with g , and that brain size under-predicts the sex difference in g by about 1.1 IQ point.

Chapter 20 – The Sociology of Psychometric and Bio-Behavioral Sciences: A Case Study of Destructive Social Reductionism and Collective Fraud in 20th Century Academia

Publisher Summary This chapter presents a case study of collective fraud in 20th century academia and the public media in connection with a demonization of Arthur Jensen. The chapter delineates some historical examples of persecution, and presents a simple model according to which Jensens change of mind from largely neutral to a more biologically based thinking about restrictions on development collides with a strong Zeitgeist of unconditional equality and strongly prohibitive notions about inheritance. The account of the attacks on Jensen is divided into the immediate reactions around 1969–1971, and the later reactions, continuing until today. Further, the chapter addresses the questions of why people were afraid to acknowledge the conservative effect of genes on human development and behavior, and why they preferred to regress to plausibility arguments rather than to reality. Moreover an account of how destructive social reductionism is presented, characterizing large parts of the 20th century, could infect many levels of academia and large parts of the public sphere with a collective fraud that, on the surface of it, looked very much like a superior moral stance in questions of equality and defense of the deprived. The chapter concludes with a simple prescription to cure the academic disease of collective fraud in academia—breaking down the egalitarian fictions and beginning again to act like scientists and demand the right to free inquiry.

Spearman's ,g, the verbal-performance balance, and brain processes: the Lynn-Vernon debate

Lynn [(1987) Personality and Individual Differences, 8, 813–844] recently treated individual, sex, and race differences in intelligence in terms of an orthodox British psychometric tradition. Verbal (V) and visuo-spatial (S) abilities, constitute, according to this line, bipolar factors but are inversely related in samples homogeneous with respect to Spearmans general factor, g. Lynns basic assumption was that the common positive V/S correlation in populations with heterogenous g reflects one physiological brain process, whereas the negative V/S correlation in populations homogenous for g has another brain basis. Vernon [(1990) Personality and Individual Differences, 11, 751–754] disagreed and set out to demonstrate, that the negative V/S correlation in samples homogenous for g is a statistical artifact. Lynn was not convinced by Vernons demonstration, and found that Vernons data provided strong support for his dual brain process theory. The present study demonstrated that the negative V/S association is a purely formal function of control for g, and illustrated why the negative V/S correlation must change from strongly negative to zero to moderately positive as g heterogeneity increases. The analysis suggests that psychometrics cannot prove brain theories of abilities, and that future studies of individual, sex, and race differences better focus more directly on individual brain development.

Test of Nyborg's General Trait Covariance (GTC) model for hormonally guided development by means of structural equation modeling

Nyborgs General Trait Covariance (GTC) model for hormonally guided development investigates the influence of gonadal hormones and fluid intelligence on body build, achievement, and socioeconomic variables. According to the model, testosterone should be negatively related to height, fat/muscle ratio, intelligence, income, and education. It is conceived that this influence should be determined to a great extent by mutual relationships between these variables. The model was tested by means of structural equation modeling (SEM) in a sample of 4375 males who had served in the United States Armed Forces. The results largely confirm Nyborgs androtype model but in addition reflect the relationships between the variables included in a quantitative causal manner. It could be shown that testosterone has a negative influence on crystallized intelligence and that this effect is mainly mediated by the negative influence of testosterone on education. An additional multiple group analysis testing for structural invariance across age groups revealed that the mediating role of education is more pronounced in old veterans. Copyright

Testosterone levels as modifiers of psychometric g

Abstract In large samples of American armed forces veterans, those below the first percentile and above the 99th percentile in serum testosterone level show significantly and considerably lower g factor scores derived from a battery of 19 diverse psychometric variables. Between these extremes of testosterone level, however, there is little relationship between testosterone and psychometric g . Factors orthogonal to g were also affected only at the extremes of testosterone level.

Critical analysis of a study on field dependence in young children.

Kojimas conclusion that our method of scoring performance in the rod-and-frame test did not produce satisfactory results in young children was invalid because our scoring method was used incorrectly, fallacious reasoning was used to reject our scoring method, subjects were classified wrongly, and the procedure used to test vertical perception in the children probably was unreliable.

Personality as Predictor of Achievement

General intelligence, g, is a powerful predictor of education, job status and income, but the predictive power of personality is less clear. The objective of the present paper was to investigate the predictive power of personality (and g) with respect to education, job status, and income. We derived Eysenckian personality factors (P, E, N, L) from MMPI data; g was distilled from a large number of highly diverse cognitive variables. Linear, nonlinear, and interaction power in predicting socioeconomic achievement in 4200+ middle-aged American males was tested. In the present study, broad personality factors provided little incremental validity to g, in predicting socioeconomic achievement across type of education and job categories. This is at odds with previous studies, and does not exclude the possibility that certain personality factors (higher or lower order) have more predictive validity within certain job categories and education types.