Height and intelligence

Last updated

The study of height and intelligence examines correlations between human height and human intelligence. Some epidemiological research on the subject has shown that there is a small but statistically significant positive correlation between height and intelligence after controlling for socioeconomic class and parental education. [1] The cited study, however, does not draw any conclusions about height and intelligence, but rather suggests "a continuing effect of post-natal growth on childhood cognition beyond the age of 9 years." This correlation arises in both the developed and developing world and persists across age groups. An individual's taller stature has been attributed to higher economic status, which often translates to a higher quality of nutrition. This correlation, however, can be inverted to characterize one's socioeconomic status as a consequence of stature, where shorter stature can attract discrimination that affects many factors, among them employment, and treatment by educators. [2] One such theory argues that since height strongly correlates with white and gray matter volume, it may act as a biomarker for cerebral development which itself mediates intelligence. [3] Competing explanations include that certain genetic factors may influence both height and intelligence, [4] [5] or that both height and intelligence may be affected in similar ways by adverse environmental exposures during development. Measurements of the total surface area and mean thickness of the cortical grey matter using a magnetic resonance imaging (MRI) revealed that the height of individuals had a positive correlation with the total cortical surface area. This supports the idea that genes that influence height also influence total surface area of the brain, which in turn influences intelligence, resulting in the correlation. [6] Other explanations further qualify the positive correlation between height and intelligence, suggesting that because the correlation becomes weaker with higher socioeconomic class and education level, environmental factors could partially override any genetic factors affecting both characteristics. [7]

Contents

Previous studies

First inquiries into the correlation of height and intelligence came within the study of development in schoolchildren. William Porter was the first person to conduct a study to find a relationship between the physiology of children and their intelligence. [8] The motive for this research was to attempt to predict the potential “dullness” or “precocity” of children based on simple measurements teachers could make. [9] He did in fact find a correlation between body size and the learning level of children, but did not focus specifically on height.

More recent studies have continued the research into a correlation between height and intelligence, but again were often not directly related to height and intelligence. Some of the earlier large studies cited for height and intelligence are the Scottish Mental Surveys in 1932 and 1947. However, the studies were largely meant to analyze the genetic and environmental contributions to cognitive ability differences. Height (and weight) were added to provide a multivariate analysis. [10]

In an effort to better understand this association, numerous other studies were thus carried out. These studies either expanded upon the association or sought to find an explanation.

A study by Douglas, et al. (1965) addressed the Scottish study and sought to test if the association reflected a linkage between development of the brain and/or emotional development and the development of the rest of the body. [11] Similarly, in 1986, Wilson et al. wanted to study if there is a longitudinal relation between height and intelligence. [12]

Nonetheless, as these studies were unable to provide satisfying results and explanations for the correlation, interest in it persists in the 21st century.

In 2014, another study was carried out by a team of researchers at Edinburgh University, Scotland, motivated by the understanding that both height and intelligence test scores are predictors of better health outcomes and mortality. The study was constructed to better identify if there are any shared phenotypic and genetic influences from height and intelligence in determining health outcomes and mortality. [13] (Be aware of the difference between genetic correlation and phenotypic correlation since the former means the proportion of heritability that two traits share while the latter just means the term that describes animals with high values for one phenotype also tending to have high (or low) values for another phenotype so to discuss over the correlation between measured height and intelligence, phenotypic correlation is what should be discussed.)

Definition of intelligence

Human intelligence can be measured according to an extensive number of tests and criteria, ranging from academic, social, and emotional fields. While there is no clear consensus on a definition of human intelligence, there are common themes among those that exist, summarized generally as "Intelligence measures an agent’s ability to achieve goals in a wide range of environments". [14] There are several theories that define different categories of intelligence and associate traits, instead of a single general ability. In most of the studies, intelligence quotient (IQ) tests were used to measure a subject's mental age, which was checked for possible correlation with height. [12] [13] While the use of IQ tests are highly debated among scientists as an accurate measurement of intelligence, they provide a quantitative and normal distribution to compare cognitive abilities among people.

Intelligence cannot be strictly defined, and it has been cautioned that intelligence has many different facets. [15] Regardless, studies conducted to compare height with intelligence frequently use the Wechsler Adult Intelligence Scale (WAIS) which measures verbal and performance abilities for individuals over the age of 16 (WISC for those under 16) years through the following tests: information, general comprehension, memory span, arithmetical reasoning, similarities, vocabulary, picture arrangement, picture completion, block design, object assembly, and a digit symbol test. [16] Many of the studies performed on the relationship between physical stature and intelligence used one of these tests in order to gauge relative cognitive ability based on the age of the participants. [17] In addition to IQ tests, some of the studies that were performed on children use academic performance as a measure of intelligence through standardized tests such as the Wide Range Achievement Test.

Correlation: studies and methodologies

A 1986 study of 13,887 American youths aged 6 to 17 years old sought to examine the correlation between height and intelligence. Height was normalized for age and sex, and intelligence was measured with the Wechsler Intelligence Scale for Children and the Wide Range Achievement Test, measuring intellectual development (IQ) and academic achievement, respectively. Subjects were re-examined 2 to 5 years later. Both the Wechsler Intelligence Scale for Children and the Wide Range Achievement Test were found to significantly correlate with height. However, change in height was found not to be correlated with IQ score. [18]

In 2000 another study found a similar correlation. 127 growth-restricted and 32 non-growth-restricted children aged 9 to 24 months were put on a two-year "randomized trial of nutritional supplementation and psychosocial stimulation." Eight years later, the subjects' growth, IQ, and cognitive functions were measured. IQ was also measured using the Wechsler Intelligence Scales. As in the 1986 study, it was found that supplementation to growth was not correlated with cognitive ability. Only psychosocial stimulation was found to increase IQ scores of subjects, and growth-restricted children had lower IQ scores than non-growth-restricted children, lending more evidence to the long-term cognitive consequences of growth restriction. [19]

These studies confirmed results found by JM Tanner in 1966. This study found that among children of school age, there is a correlation of about 0.15-0.25 between height and score on the 11+ test, an examination administered to students in England. It was found that this correlation decreases with age, but does not completely disappear; in samples of young adults, correlations of up to 0.2 were found. This study also found that “the greater the number of children in the family the lower their height and the less their scores in mental tests”, and attributes the effect “to co-advancement [of height and cognitive ability] and disappears when maturity is reached.” The correlation between number of children and intelligence was found to be stronger in poor families than in rich ones, which contributed to the conclusion that there is a strong correlation between height and mental ability between children in different socio-economic groups that persists in adulthood. [8]

A study was done by the Newcastle Thousands Families in 1947 to see if there was a correlation between birth weights and IQ at ages 9 and 13. There showed no correlation between birth weights and their IQs. However, height at the age of 9 played a major role in the IQ of the children (standardized regression coefficient b = 2.6, 95% CI 1.6-3.6, P < 0.0001). At the ages of 13, social economics played yet another larger role (b = 3.4, 95% CI 2.3-4.4, P = 0.001). [1]

With data from ten consecutive years of quantitative measurements on height and intelligence separated by girls and boys and gathered from the Harvard Growth Study, this compilation of analyses shows the difference in correlation between height and intelligence in the classes of girls and boys. Boys demonstrate no clear correlation between height at a certain age group and intelligence later on in life but girls do. There appears to be a clear link between intelligence levels at 10 and 11 with a girl's height at the ages of 8 and 9 with other variables of note, i.e., socioeconomic status, age of first menstruation and ethnicity factoring into the correlation as well. [20]

A 1999 study that was conducted on a sample on 32,887 Swedish men, aged 18, free of growth defects showed that, by and large, shorter men (with 2 standard deviations below the mean) demonstrated poorer physical and psychological performance in the context of military service, with increased risk of musculoskeletal diagnoses. Additionally, increased height showed a relationship with increased mean intellectual performance and, under conditions of stress, shorter men showcased demonstrably worse leadership capability and psychological function. [21]

A 2011 model which incorporated assortative mating patterns into a bivariate model was used to account for height-to-intelligence factors that related to these mating habits as well as pleiotropic genetic influences when establishing the correlation between height and intelligence. Additionally, this team of researchers was responsible for using a dataset aggregated for Swedish male twins to explain both the genetic and environmental influences of the relationship between height and intelligence and height and capability to manage wartime stress. [22]

In 1989 the heights of male and female corporate managers and non-managers were measured in two studies with about 200 subjects. Both studies found a statistically significant correlation between managerial position and height; taller people were more likely to hold managerial positions, regardless of sex. [23]

A 2005 study used data on 1,181 identical twins and 1,412 fraternal twins, collected from Norwegian army files and Norwegian twin registries, in order to factor the correlation between intelligence test scores and standing height into environmental and genetic components. It used a structural equation model comparing the correlation between genetic, shared environmental and non-shared environmental factors and found that 59% of the height-intelligence correlation was due to shared environmental factors. Genes were found to contribute 35% of the correlation, and non-shared environmental factors contributed 6%, both statistically significant amounts. [24]

A 1991 study conducted on 76,111 Danish men sought to test the height-intelligence positive correlation on either extremes of height. The study defined two groups: the short group, composed of individuals below the 2nd percentile for height and the tall group, composed of individuals above the 98th percentile for height in Denmark. It found that the short group's intelligence test score and educational level means lay about two-thirds of a standard deviation below the overall means, but suggested there appeared to be local factors that may have contributed negatively and significantly to the scores. In contrast, the study found the tall group scored about one-half standard deviation above the overall means, but suggested that both groups scored below what would be expected from a linear trend. [7]

A study from 1985 to 2005 was conducted on Dutch twin pairs from the ages 5 to 18 to establish a correlation factor. There was shown a positive correlation in childhood and early adolescence. These factors were used to gauge the intelligence in adults. The contributing factors for this study were mainly just genetics and full-scaled IQ. [25]

There was weak or no correlation between cognitive ability and height found when examining ten brain measurements from a large elderly population, even when controlled for sex and age. [26] Even though height and brain size are highly influenced by genes, doubt is raised about the relationship between them when considering that the correlation between height and cognitive ability is not steady throughout life. [26] There is an increase in brain development during the adolescent years and a marked decrease afterwards, despite height generally staying constant after reaching adulthood. [26]

Explanations of the correlation

An individual's height is determined by a complex interplay between genes and environment. Statistical analysis of multiple research studies have produced a correlation between height and intelligence. Various genetic and environmental factors may influence height, and the reasons are sought for any correlation with measured intelligence.

It has been suggested that increases in average height, in response to improved nutrition, have been accompanied by an increase in brain size, and is one explanation for an overall rise in measured intelligence among all tested populations that has been called the Flynn effect. [27]

Heritability estimates for height can be generated using comparisons among close relatives, such as between parents and children or siblings. To measure the effect of genetic inheritance, height comparisons are correlated with total shared genetic markers. Common percent values range between 60 and 80%, [28] with high variation attributed to differences in a population's genetic history and environment (such as climate, nutrition, and lifestyle).

The most notable contributing environmental influences associated with the correlation of height and IQ include “diet, disease, psychosocial stress and inadequate cognitive stimulation” [29] Populations that live under stable conditions tend to have higher values of genetic influence, while populations susceptible to events of poor nutrition and illness show greater determination from their environment. [30]

An auxological approach that emphasizes multiple influences from all aspects of life, with special attention paid to prenatal and very early child development, seem to offer the most robust and accurate portrayal of overall growth and development. From these perspectives, we can better understand if the correlation persists, especially within developing countries prone to environmental uncertainties. [31]

Height and intelligence may be correlated, but there is not significant proof of it being caused by genetics. There are many genes associated with genetic transmission of intelligence, but current theories of intelligence point to inheritance of intelligence from parents to be due to both genetic and environmental factors, especially as there is no concrete proof of the relationship between certain genes and intelligence. [32]

There is evidence that intellectual development is influenced by the expectations placed on an individual. [33] In an experiment involving elementary school children, researchers found that when teachers believe students are above average intellect, these students tend to do better in school and receive higher IQ scores than students who are perceived as average or below average intellect, regardless of the actual competence of the students. This self-fulfilling prophecy caused by expectations is known as the Pygmalion effect, [33] and it may play have an effect on taller student who are generally viewed as more mature or dominant. [34]

Sexual selection and cross-trait assortative mating might also contribute to the correlation between height and intelligence. [35] Because both height and intelligence positively affect an individual's overall fitness, individuals generally look for these traits in potential partners. In other words, smart men are more likely to mate with tall women, and smart women are more likely to mate with tall men, as both traits are affected by perceptions of cross-trait attractiveness. [35]

Statistics

Across studies, the correlation coefficient of height and intelligence was generally found to be around 0.2, [22] [36] [37] [38] indicating a positive association between height and intelligence which is weak but still statistically significant. A smaller within-family height-intelligence correlation of 0.10 was also found, indicating that both assortative mating and pleiotropy may be contributing causes for the general correlation. [22]

Height and intelligence are both polygenic traits, and as a result it is difficult to isolate possible causes for the variation in each of these traits individually, let alone causes for correlations between them. [22] Results regarding the relative responsibility of genetic and environmental factors in causing the correlation are far from conclusive; while some studies have arrived at similar estimates of the relative responsibility of genetic vs. environmental factors, [22] [36] others have arrived at completely different estimates. [37]

It's also important to note that several of the recent studies confirming the correlation employed the standard bivariate ACE model, [22] [36] [37] which is extremely sensitive to assumptions reflected in parameters. For instance, two of these studies arrived at similar estimates for the relative responsibility of common environmental and genetic factors in causing the correlation: 59% and 59% for the former, 31% and 35% for the latter. [22] [36] However, only slight modifications to the coefficient of assortative mating made the difference between the inferred percentage of genetic responsibility being as low as around 30% (the value the authors reported) to as high as 90%. [22] Further, another study using the same model even concluded that genetics alone could explain the correlation, without any influence from common environmental factors such as one's education level and nutrition. [22] [39] This could have been because the studied population was relatively economically egalitarian, meaning access to resources like education and nutrition played less of a role than they might in other populations, or because of differences in how the researches handled the model and its parameters. [37] The ACE model used in these studies was found to be sensitive to assumptions of assortative mating; results should therefore be interpreted with caution, as should the resulting percentages of genetic vs. environmental contribution. [22]

See also

Related Research Articles

<span class="mw-page-title-main">Intelligence quotient</span> Score from a test designed to assess intelligence

An intelligence quotient (IQ) is a total score derived from a set of standardised tests or subtests designed to assess human intelligence. The abbreviation "IQ" was coined by the psychologist William Stern for the German term Intelligenzquotient, his term for a scoring method for intelligence tests at University of Breslau he advocated in a 1912 book.

Discussions of race and intelligence – specifically regarding claims of differences in intelligence along racial lines – have appeared in both popular science and academic research since the modern concept of race was first introduced. With the inception of IQ testing in the early 20th century, differences in average test performance between racial groups were observed, though these differences have fluctuated and in many cases steadily decreased over time. Complicating the issue, modern science has concluded that race is a socially constructed phenomenon rather than a biological reality, and there exist various conflicting definitions of intelligence. In particular, the validity of IQ testing as a metric for human intelligence is disputed. Today, the scientific consensus is that genetics does not explain differences in IQ test performance between groups, and that observed differences are environmental in origin.

Nature versus nurture is a long-standing debate in biology and society about the relative influence on human beings of their genetic inheritance (nature) and the environmental conditions of their development (nurture). The alliterative expression "nature and nurture" in English has been in use since at least the Elizabethan period and goes back to medieval French. The complementary combination of the two concepts is an ancient concept. Nature is what people think of as pre-wiring and is influenced by genetic inheritance and other biological factors. Nurture is generally taken as the influence of external factors after conception e.g. the product of exposure, experience and learning on an individual.

Twin studies are studies conducted on identical or fraternal twins. They aim to reveal the importance of environmental and genetic influences for traits, phenotypes, and disorders. Twin research is considered a key tool in behavioral genetics and in related fields, from biology to psychology. Twin studies are part of the broader methodology used in behavior genetics, which uses all data that are genetically informative – siblings studies, adoption studies, pedigree, etc. These studies have been used to track traits ranging from personal behavior to the presentation of severe mental illnesses such as schizophrenia.

Human intelligence is the intellectual capability of humans, which is marked by complex cognitive feats and high levels of motivation and self-awareness. Using their intelligence, humans are able to learn, form concepts, understand, and apply logic and reason. Human intelligence is also thought to encompass our capacities to recognize patterns, plan, innovate, solve problems, make decisions, retain information, and use language to communicate.

The g factor is a construct developed in psychometric investigations of cognitive abilities and human intelligence. It is a variable that summarizes positive correlations among different cognitive tasks, reflecting the fact that an individual's performance on one type of cognitive task tends to be comparable to that person's performance on other kinds of cognitive tasks. The g factor typically accounts for 40 to 50 percent of the between-individual performance differences on a given cognitive test, and composite scores based on many tests are frequently regarded as estimates of individuals' standing on the g factor. The terms IQ, general intelligence, general cognitive ability, general mental ability, and simply intelligence are often used interchangeably to refer to this common core shared by cognitive tests. However, the g factor itself is a mathematical construct indicating the level of observed correlation between cognitive tasks. The measured value of this construct depends on the cognitive tasks that are used, and little is known about the underlying causes of the observed correlations.

<span class="mw-page-title-main">Human behaviour genetics</span> Field that examines the role of genetic and environmental influences on human behaviour

Human behaviour genetics is an interdisciplinary subfield of behaviour genetics that studies the role of genetic and environmental influences on human behaviour. Classically, human behavioural geneticists have studied the inheritance of behavioural traits. The field was originally focused on determining the importance of genetic influences on human behaviour. It has evolved to address more complex questions such as: how important are genetic and/or environmental influences on various human behavioural traits; to what extent do the same genetic and/or environmental influences impact the overlap between human behavioural traits; how do genetic and/or environmental influences on behaviour change across development; and what environmental factors moderate the importance of genetic effects on human behaviour. The field is interdisciplinary, and draws from genetics, psychology, and statistics. Most recently, the field has moved into the area of statistical genetics, with many behavioural geneticists also involved in efforts to identify the specific genes involved in human behaviour, and to understand how the effects associated with these genes changes across time, and in conjunction with the environment.

Neuroscience and intelligence refers to the various neurological factors that are partly responsible for the variation of intelligence within species or between different species. A large amount of research in this area has been focused on the neural basis of human intelligence. Historic approaches to studying the neuroscience of intelligence consisted of correlating external head parameters, for example head circumference, to intelligence. Post-mortem measures of brain weight and brain volume have also been used. More recent methodologies focus on examining correlates of intelligence within the living brain using techniques such as magnetic resonance imaging (MRI), functional MRI (fMRI), electroencephalography (EEG), positron emission tomography and other non-invasive measures of brain structure and activity.

Hereditarianism is the doctrine or school of thought that heredity plays a significant role in determining human nature and character traits, such as intelligence and personality. Hereditarians believe in the power of genetics to explain human character traits and solve human social and political problems. Hereditarians adopt the view that an understanding of human evolution can extend the understanding of human nature.

Research on the heritability of IQ inquires into the degree of variation in IQ within a population that is due to genetic variation between individuals in that population. There has been significant controversy in the academic community about the heritability of IQ since research on the issue began in the late nineteenth century. Intelligence in the normal range is a polygenic trait, meaning that it is influenced by more than one gene, and in the case of intelligence at least 500 genes. Further, explaining the similarity in IQ of closely related persons requires careful study because environmental factors may be correlated with genetic factors.

Intelligence: Knowns and Unknowns is a report about scientific findings on human intelligence, issued in 1995 by a task force created by the Board of Scientific Affairs of the American Psychological Association (APA) following the publication of The Bell Curve and the scholarly debate that followed it. The report was subsequently published in the February 1996 issue of the peer-reviewed journal American Psychologist.

Health can affect intelligence in various ways. Conversely, intelligence can affect health. Health effects on intelligence have been described as being among the most important factors in the origins of human group differences in IQ test scores and other measures of cognitive ability. Several factors can lead to significant cognitive impairment, particularly if they occur during pregnancy and childhood when the brain is growing and the blood–brain barrier of the child is less effective. Such impairment may sometimes be permanent, sometimes be partially or wholly compensated for by later growth.

Environment and intelligence research investigates the impact of environment on intelligence. This is one of the most important factors in understanding human group differences in IQ test scores and other measures of cognitive ability. It is estimated that genes contribute about 20–40% of the variance in intelligence in childhood and about 80% in adulthood. Thus the environment and its interaction with genes account for a high proportion of the variation in intelligence seen in groups of young children, and for a small proportion of the variation observed in groups of mature adults. Historically, there has been great interest in the field of intelligence research to determine environmental influences on the development of cognitive functioning, in particular, fluid intelligence, as defined by its stabilization at 16 years of age. Despite the fact that intelligence stabilizes in early adulthood it is thought that genetic factors come to play more of a role in our intelligence during middle and old age and that the importance of the environment dissipates.

In multivariate quantitative genetics, a genetic correlation is the proportion of variance that two traits share due to genetic causes, the correlation between the genetic influences on a trait and the genetic influences on a different trait estimating the degree of pleiotropy or causal overlap. A genetic correlation of 0 implies that the genetic effects on one trait are independent of the other, while a correlation of 1 implies that all of the genetic influences on the two traits are identical. The bivariate genetic correlation can be generalized to inferring genetic latent variable factors across > 2 traits using factor analysis. Genetic correlation models were introduced into behavioral genetics in the 1970s–1980s.

Behavioural genetics, also referred to as behaviour genetics, is a field of scientific research that uses genetic methods to investigate the nature and origins of individual differences in behaviour. While the name "behavioural genetics" connotes a focus on genetic influences, the field broadly investigates the extent to which genetic and environmental factors influence individual differences, and the development of research designs that can remove the confounding of genes and environment. Behavioural genetics was founded as a scientific discipline by Francis Galton in the late 19th century, only to be discredited through association with eugenics movements before and during World War II. In the latter half of the 20th century, the field saw renewed prominence with research on inheritance of behaviour and mental illness in humans, as well as research on genetically informative model organisms through selective breeding and crosses. In the late 20th and early 21st centuries, technological advances in molecular genetics made it possible to measure and modify the genome directly. This led to major advances in model organism research and in human studies, leading to new scientific discoveries.

Malleability of intelligence describes the processes by which intelligence can increase or decrease over time and is not static. These changes may come as a result of genetics, pharmacological factors, psychological factors, behavior, or environmental conditions. Malleable intelligence may refer to changes in cognitive skills, memory, reasoning, or muscle memory related motor skills. In general, the majority of changes in human intelligence occur at either the onset of development, during the critical period, or during old age.

Neuroimaging intelligence testing concerns the use of neuroimaging techniques to evaluate human intelligence. Neuroimaging technology has advanced such that scientists hope to use neuroimaging increasingly for investigations of brain function related to IQ.

The relationship between intelligence and education is one that scientists have been studying for years.

Adoption studies typically compare pairs of persons, e.g., adopted child and adoptive mother or adopted child and biological mother, to assess genetic and environmental influences on behavior. These studies are one of the classic research methods of behavioral genetics. The method is used alongside twin studies to identify the roles of genetics and environmental variables that impact intelligence, and behavioral disorders.

In behavioral genetics, the Scarr–Rowe effect, also known as the Scarr–Rowe hypothesis, refers to the proposed moderating effect of low socioeconomic status on the heritability of children's IQ. According to this hypothesis, lower socioeconomic status and greater exposure to social disadvantage during childhood leads to a decrease in the heritability of IQ, as compared to children raised in more advantaged environments. It is considered an example of gene–environment interaction. This hypothesized effect was first proposed by Sandra Scarr, who found support for it in a 1971 study of twins in Philadelphia, and these results were replicated by David C. Rowe in 1999. Since then, similar results have been replicated numerous times, though not all replication studies have yielded positive results. A 2015 meta-analysis found that the effect was predominant in the United States while less evident in societies with robust child welfare systems.

References

  1. 1 2 Pearce MS, Deary IJ, Young AH, Parker L (June 2005). "Growth in early life and childhood IQ at age 11 years: the Newcastle Thousand Families Study". International Journal of Epidemiology. 34 (3): 673–7. doi: 10.1093/ije/dyi038 . PMID   15746206.
  2. Tyrrell J, Jones SE, Beaumont R, Astley CM, Lovell R, Yaghootkar H, et al. (March 2016). "Height, body mass index, and socioeconomic status: mendelian randomisation study in UK Biobank". BMJ. 352: i582. doi:10.1136/bmj.i582. PMC   4783516 . PMID   26956984.
  3. Taki Y, Hashizume H, Sassa Y, Takeuchi H, Asano M, Asano K, Kotozaki Y, Nouchi R, Wu K, Fukuda H, Kawashima R (January 2012). "Correlation among body height, intelligence, and brain gray matter volume in healthy children". NeuroImage. 59 (2): 1023–7. doi:10.1016/j.neuroimage.2011.08.092. PMID   21930215. S2CID   25227802.
  4. Silventoinen K, Posthuma D, van Beijsterveldt T, Bartels M, Boomsma DI (November 2006). "Genetic contributions to the association between height and intelligence: Evidence from Dutch twin data from childhood to middle age" (PDF). Genes, Brain and Behavior. 5 (8): 585–95. doi: 10.1111/j.1601-183X.2006.00208.x . PMID   17081263. S2CID   11248397.
  5. Sniekers S, Stringer S, Watanabe K, Jansen PR, Coleman JR, Krapohl E, Taskesen E, Hammerschlag AR, Okbay A, Zabaneh D, Amin N, Breen G, Cesarini D, Chabris CF, Iacono WG, Ikram MA, Johannesson M, Koellinger P, Lee JJ, Magnusson PK, McGue M, Miller MB, Ollier WE, Payton A, Pendleton N, Plomin R, Rietveld CA, Tiemeier H, van Duijn CM, Posthuma D (July 2017). "Genome-wide association meta-analysis of 78,308 individuals identifies new loci and genes influencing human intelligence". Nature Genetics. 49 (7): 1107–1112. doi:10.1038/ng.3869. PMC   5665562 . PMID   28530673.
  6. Vuoksimaa E, Panizzon MS, Franz CE, Fennema-Notestine C, Hagler DJ, Lyons MJ, et al. (September 2018). "Brain structure mediates the association between height and cognitive ability". Brain Structure & Function. 223 (7): 3487–3494. doi:10.1007/s00429-018-1675-4. PMC   6425087 . PMID   29748873.
  7. 1 2 Teasdale TW, Sørensen TI, Owen DR (May 1989). "Fall in association of height with intelligence and educational level". BMJ. 298 (6683): 1292–3. doi:10.1136/bmj.298.6683.1292. PMC   1836522 . PMID   2500201.
  8. 1 2 Tanner JM (September 1966). "Galtonian eugenics and the study of growth: the relation of body size, intelligence test score, and social circumstances in children and adults". The Eugenics Review. 58 (3): 122–35. PMC   2982386 . PMID   5913725.
  9. Porter W (1893). "The Physical Basis of Precocity and Dullness". Transactions of the Academy of Science of St. Louis. 6 (7): 161–181.
  10. Benyamin B, Wilson V, Whalley LJ, Visscher PM, Deary IJ (September 2005). "Large, consistent estimates of the heritability of cognitive ability in two entire populations of 11-year-old twins from Scottish mental surveys of 1932 and 1947". Behavior Genetics. 35 (5): 525–34. CiteSeerX   10.1.1.512.1480 . doi:10.1007/s10519-005-3556-x. PMID   16184482. S2CID   9289733.
  11. Douglas JW, Ross JM, Simpson HR (May 1965). "The relation between height and measured educational ability in school children of the same social class, family size and stage of sexual development". Human Biology. 37: 178–86. PMID   14325451.
  12. 1 2 Wilson DM, Hammer LD, Duncan PM, Dornbusch SM, Ritter PL, Hintz RL, Gross RT, Rosenfeld RG (October 1986). "Growth and intellectual development". Pediatrics. 78 (4): 646–50. doi:10.1542/peds.78.4.646. PMID   3763275. S2CID   23736174.
  13. 1 2 Marioni RE, Batty GD, Hayward C, Kerr SM, Campbell A, Hocking LJ, et al. (March 2014). "Common genetic variants explain the majority of the correlation between height and intelligence: the generation Scotland study". Behavior Genetics. 44 (2): 91–6. doi:10.1007/s10519-014-9644-z. PMC   3938855 . PMID   24554214.
  14. Legg S, Hutter M (2007). "A collection of definitions of intelligence". Advances in Artificial General Intelligence: Concepts, Architectures and Algorithms. Amsterdam: IOS Press. p. 9.
  15. Van der Maas HL, Kan K, Borsboom D (March 2014). "Intelligence Is What the Intelligence Test Measures. Seriously". Journal of Intelligence. 2 (1): 12–15. doi: 10.3390/jintelligence2010012 .
  16. Wechsler D (1958). The Measurement and Appraisal of Adult Intelligence (4th ed.). doi:10.1037/11167-000.
  17. Walker SP, Grantham-Mcgregor SM, Powell CA, Chang SM (July 2000). "Effects of growth restriction in early childhood on growth, IQ, and cognition at age 11 to 12 years and the benefits of nutritional supplementation and psychosocial stimulation". The Journal of Pediatrics. 137 (1): 36–41. doi:10.1067/mpd.2000.106227. PMID   10891819.
  18. Wilson DM, Hammer LD, Duncan PM, Dornbusch SM, Ritter PL, Hintz RL, et al. (October 1986). "Growth and intellectual development". Pediatrics. 78 (4): 646–50. doi:10.1542/peds.78.4.646. PMID   3763275. S2CID   23736174.
  19. Walker SP, Grantham-Mcgregor SM, Powell CA, Chang SM (July 2000). "Effects of growth restriction in early childhood on growth, IQ, and cognition at age 11 to 12 years and the benefits of nutritional supplementation and psychosocial stimulation". The Journal of Pediatrics. 137 (1): 36–41. doi:10.1067/mpd.2000.106227. PMID   10891819.
  20. Humphreys LG, Davey TC, Park RK (December 1985). "Longitudinal correlation analysis of standing height and intelligence". Child Development. 56 (6): 1465–78. doi:10.1111/j.1467-8624.1985.tb00212.x. PMID   4075869.
  21. Tuvemo T, Jonsson B, Persson I (1999-01-01). "Intellectual and physical performance and morbidity in relation to height in a cohort of 18-year-old Swedish conscripts". Hormone Research. 52 (4): 186–91. doi:10.1159/000023459. PMID   10725784. S2CID   24866229.
  22. 1 2 3 4 5 6 7 8 9 10 Beauchamp JP, Cesarini D, Johannesson M, Lindqvist E, Apicella C (March 2011). "On the sources of the height-intelligence correlation: new insights from a bivariate ACE model with assortative mating". Behavior Genetics. 41 (2): 242–52. doi:10.1007/s10519-010-9376-7. PMC   3044837 . PMID   20603722.
  23. Egolf DB, Corder LE (1991). "Height differences of low and high job status, female and male corporate employees". Sex Roles. 24 (5–6): 365–373. doi:10.1007/BF00288309. ISSN   0360-0025. S2CID   145223126.
  24. Sundet JM, Tambs K, Harris JR, Magnus P, Torjussen TM (2005-08-01). "Resolving the Genetic and Environmental Sources of the Correlation Between Height and Intelligence: A Study of Nearly 2600 Norwegian Male Twin Pairs". Twin Research and Human Genetics. 8 (4): 307–311. doi: 10.1375/twin.8.4.307 . ISSN   1839-2628. PMID   16176713.
  25. Silventoinen K, Posthuma D, van Beijsterveldt T, Bartels M, Boomsma DI (November 2006). "Genetic contributions to the association between height and intelligence: Evidence from Dutch twin data from childhood to middle age" (PDF). Genes, Brain and Behavior. 5 (8): 585–95. doi: 10.1111/j.1601-183X.2006.00208.x . PMID   17081263. S2CID   11248397.
  26. 1 2 3 Jäncke L, Liem F, Merillat S (November 2019). "Weak correlations between body height and several brain metrics in healthy elderly subjects" (PDF). The European Journal of Neuroscience. 50 (10): 3578–3589. doi:10.1111/ejn.14501. PMID   31278790. S2CID   195813889.
  27. Neisser U, Boodoo G, Bouchard Jr TJ, Boykin AW, Brody N, Ceci SJ, Halpern DF, Loehlin JC, Perloff R, Sternberg RJ, Urbina S (1996). "Intelligence: Knowns and unknowns". American Psychologist. 51 (2): 77–101. doi:10.1037/0003-066x.51.2.77.
  28. "How much of human height is genetic and how much is due to nutrition?". Scientific American. Retrieved 2016-11-16.
  29. Gale C (June 2005). "Commentary: Height and intelligence". International Journal of Epidemiology. 34 (3): 678–9. doi: 10.1093/ije/dyi064 . PMID   15831563.
  30. Colom R, Lluis-Font JM, Andrés-Pueyo A (2005-01-01). "The generational intelligence gains are caused by decreasing variance in the lower half of the distribution: Supporting evidence for the nutrition hypothesis". Intelligence. 33 (1): 83–91. doi:10.1016/j.intell.2004.07.010.
  31. Lampl M, Mummert A, Schoen M (October 2015). "Auxological perspectives on 'growth' in DOHaD". Journal of Developmental Origins of Health and Disease. 6 (5): 390–8. doi:10.1017/S2040174415001403. PMID   26268724. S2CID   5189046.
  32. McAskie M, Clarke AM (May 1976). "Parent-offspring resemblances in intelligence: theories and evidence". British Journal of Psychology. 67 (2): 243–73. doi:10.1111/j.2044-8295.1976.tb01514.x. PMID   779915.
  33. 1 2 Rosenthal R, Jacobson L (1968). "Pygmalion in the classroom". The Urban Review. 3 (1): 16–20. doi:10.1007/BF02322211. ISSN   0042-0972. S2CID   189835367.
  34. Schank R (1994). Beliefs, Reasoning, and Decision Making: Psycho-Logic in Honor of Bob Abelson. Psychology Press. p. 319.
  35. 1 2 Keller MC, Garver-Apgar CE, Wright MJ, Martin NG, Corley RP, Stallings MC, et al. (April 2013). "The genetic correlation between height and IQ: shared genes or assortative mating?". PLOS Genetics. 9 (4): e1003451. doi: 10.1371/journal.pgen.1003451 . PMC   3617178 . PMID   23593038.
  36. 1 2 3 4 Sundet JM, Tambs K, Harris JR, Magnus P, Torjussen TM. Resolving the genetic and environmental sources of the correlation between height and intelligence: a study of nearly 2600 Norwegian male twin pairs. Twin Res Hum Genet. 2005 Aug;8(4):307-11
  37. 1 2 3 4 Silventoinen K, Posthuma D, van Beijsterveldt T, Bartels M, Boomsma DI (November 2006). "Genetic contributions to the association between height and intelligence: Evidence from Dutch twin data from childhood to middle age" (PDF). Genes, Brain and Behavior. 5 (8): 585–95. doi: 10.1111/j.1601-183X.2006.00208.x . PMID   17081263. S2CID   11248397.
  38. Tanner JM. Relation of body size, intelligence test scores and social circumstances. In: Mussen PH, Largen J, Covington M (eds). Trends and Issues in Developmental Psychology. New York: Holt, Rinehard and Winston Inc., 1969.
  39. Harris MA, Brett CE, Deary IJ, Starr JM (September 2016). "Associations among height, body mass index and intelligence from age 11 to age 78 years". BMC Geriatrics. 16 (1): 167. doi: 10.1186/s12877-016-0340-0 . PMC   5041406 . PMID   27681526.