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Relations between average temperature of each of the 48 contiguous states and estimates of state IQ were inspected. Additional state variables were controlled in the correlational analyses, namely gross state product, percent Hispanic, Black, and Asian in the state population, and the pupil-to-teacher ratio for each state. A significant correlation between average temperature and state IQ was found (r = -.70, p < .001). Possible explanations are discussed. DOI 10.2466/04.17.PR0.107.4.251-254

BACKGROUND: Recently, in a cross-sectional study of 201 children in Araihazar, Bangladesh, exposure to arsenic (As) in drinking water has been shown to lower the scores on tests that measure [...]

An attempt is made to find out whether persons in colder climates tend to have higher IQs than persons in warmer climates and for this, mean IQ of 129 countries were correlated with per capita income, skin color, and winter and summer temperatures, conceptualizing skin color as a multigenerational reflection of climate. The findings were viewed as congruent with, although not providing unequivocal evidence for, the contention that higher intelligence evolves in colder climates.

Lead in the body may adversely affect a child's intellectual development even when it is below 10 micrograms per deciliter, according to a study of 172 children tested from six months of age up to five years. The Centers for Disease Control and Prevention believes this level of lead is relatively harmless, but children with this level still had lower IQs than normal. In fact, the impact of lead on IQ was actually greater at the lower concentration than at higher concentrations.

BACKGROUND: Although prenatal methylmercury exposure has been linked to poorer intellectual function in several studies, data from two major prospective, longitudinal studies yielded contradictory results. Associations with cognitive deficits were reported in a Faroe Islands cohort, but few were found in a study in the Seychelles Islands. It has been suggested that co-exposure to another contaminant, polychlorinated biphenyls (PCBs), may be responsible for the positive findings in the former study and that co-exposure to nutrients in methylmercury-contaminated fish may have obscured and/or protected against adverse effects in the latter. OBJECTIVES: We aimed to determine the degree to which co-exposure to PCBs may account for the adverse effects of methylmercury and the degree to which co-exposure to docosahexaenoic acid (DHA) may obscure these effects in a sample of Inuit children in Arctic Quebec. METHODS: IQ was estimated in 282 school-age children from whom umbilical cord blood samples had been obtained and analyzed for mercury and other environmental exposures. RESULTS: Prenatal mercury exposure was related to poorer estimated IQ after adjustment for potential confounding variables. The entry of DHA into the model significantly strengthened the association with mercury, supporting the hypothesis that beneficial effects from DHA intake can obscure adverse effects of mercury exposure. Children with cord mercury [greater than or equal to] 7.5 µg/L were four times as likely to have an IQ score < 80, the clinical cut-off for borderline intellectual disability. Co-exposure to PCBs did not alter the association of mercury with IQ. CONCLUSIONS: To our knowledge, this is the first study to document an association of prenatal mercury exposure with poorer performance on a school-age assessment of IQ, a measure whose relevance for occupational success in adulthood is well established. This association was seen at levels in the range within which many U.S. children of Asian-American background are exposed., Introduction The developmental neurotoxicity of methylmercury first became evident in the midtwentieth century when infants born to women who had eaten heavily contaminated fish in Minimata Bay, Japan (Harada 1995) [...]

Although adverse consequences of poverty for children are documented widely, little is understood about the mechanisms through which the effects of poverty disadvantage young children. In this analysis we investigate multiple mechanisms through which poverty affects a child's intellectual development. Using data from the NLSY and structural equation models, we have constructed five latent factors (cognitive stimulation, parenting style, physical environment, child's ill health at birth, and ill health in childhood) and have allowed these factors, along with child care, to mediate the effects of poverty and other exogenous variables. We produce two main findings. First, the influence of family poverty on children's intellectual development is mediated completely by the intervening mechanisms measured by our latent factors. Second, our analysis points to cognitive stimulation in the home, and (to a lesser extent) to parenting style, physical environment of the home, and poor child health at birth, as mediating factors that are affected by lack of income and that influence children's intellectual development.

Traditional theories of psychology have held that a child's personality is greatly influenced by the parents' child-rearing style. However, recent studies have suggested the opposite, indicating an absence of effect on the long-term personality of the child, regardless of whether the parents are authoritarian or liberal, punitive or permissive, and sociable or withdrawn. Whatever effects are exerted by child-rearing practices, they appear to occur before puberty. Another issue is the effect of upbringing on intelligence; research suggests that child-rearing style has more influence on intelligence than on personality. This study was designed to test the theory that the family environment does affect intelligence more than personality. The subjects were 386 pairs of young adolescent (ages 11 to 16) Irish siblings. They were given a vocabulary test and a personality inventory. The correlations between siblings were as follows: 0.48 for intelligence, 0.31 for extraversion, 0.14 for psychoticism, and 0.06 for neuroticism. This indicates that the correlations for the three personality traits were considerably lower than the correlation for intelligence. Since the three personality-trait correlations vary in magnitude, they may result from different combinations of genetic and environmental factors. Based on the low correlations, it was concluded that neuroticism and psychoticism were not influenced by the shared family environment. The authors concluded that environment does appear to influence extraversion, and even more strongly, intelligence, but genetic factors probably contribute to the correlations between siblings as well. (Consumer Summary produced by Reliance Medical Information, Inc.)

Both genes and the environment play a role in the development of intelligence. A study in France involving adopted children shows that the intelligence quotient (IQ) of children is influenced by both genetic background and environmental circumstances. The study was carefully controlled, using children in the same approximate age group and sharing the same approximate age of adoption. Studying adopted children allowed separation of genetic and environmental influences. Adopted children who were raised by parents with a high socioeconomic status had IQ levels approximately 12 points higher than children raised by parents of low socioeconomic status, regardless of the children's genetic or biological backgrounds. The occupations of the two groups of parents were as extreme in socioeconomic status as possible. This shows the environmental effect in the development of intelligence. Adopted children born to parents of high socioeconomic status had IQ levels that were approximately 15 points higher than children born to parents of low socioeconomic backgrounds, regardless of the socioeconomic status of the adoptive parents. This shows the genetic effect on intelligence, but can not preclude prenatal effects, influences on the children before they were born. No interaction was seen between the environmental and genetic effects. Changes in IQ from environmental influences or genetic influences occur independently from each other, yet both affect IQ levels.