Familial Studies of Intelligence: A Review

Abstract

A summary of 111 studies identified in a survey of the world literature on familial resemblances in measured intelligence reveals a profile of average correlations consistent with a polygenic mode of inheritance. There is, however, a marked degree of heterogeneity of the correlations within familial groupings, which is not moderated by sex of familial pairing or by type of intelligence test used.

Resemblance of psychotic symptoms and syndromes in affected sibling pairs from the Irish Study of High-Density Schizophrenia Families: evidence for possible etiologic heterogeneity

“…The direct influence of illness characteristics of one sibling on another cannot be ruled out. Second, sibling resemblance might be due to genetically influenced multifactorial characteristics such as temperament (67) or intellect (68). For example, individuals high in emotionality may be particularly prone to depressive symptoms during a schizophrenic illness, while those low in intelligence might be more prone to a poor outcome.…”

Genetic and Environmental Contributions to General Cognitive Ability Through the First 16 Years of Life.

“…The nonshared environment is significant throughout the life span. Indeed, these findings are some of the most consistent and highly replicated in the psychological literature (e.g., Alarcon, Plomin, Fulker, Corley, & DeFries, 1998;Bouchard & McGue, 1981;Cardon, Fulker, DeFries, & Plomin, 1992;Mackintosh, 1998;Plomin, Fulker, Corley, & DeFries, 1997;Reznick, Corley, & Robinson, 1997;Rice, Carey, Fulker, & DeFries, 1989;Skodak & Skeels, 1949;Snyderman & Rothman, 1998;Wilson, 1983). As a result, few contemporary scientists seriously engage in nature versus nurture debates or dispute the overwhelming finding that cognitive ability involves both genetic and environmental influences.…”

Recent Developments in Intergenerational Mobility

“…57 There are large literatures in some of these areas and, by necessity, we have had to omit many interesting papers in this brief overview. 58 Bouchard and McGue (1981) Bjorklund, Eriksson and Jantti (2010) use similar data from Sweden to extend this work, looking at both intergenerational and sibling correlations in IQ. They find a similar estimate of intergenerational correlation to that of Black, Devereux, and Salvanes.…”