In this article, it is argued that it makes sense to define and distinguish three levels of human intelligence: intelligence as genotypical potential, intelligence as actualised in environmental interaction, and intelligence as measured by tests (IQ). This raises the questions of what is meant by the term "intelligence as potential", and…

Scores on a mental development scale were correlated for 8-month-old twins and other sibling pairs. Greater correlations were found between twins than sibling pairs. (ST)

Studies by the late English psychologist Cyril Burt of IQ scores of separated twins strongly suggested that intelligence was inherited. A summary of recent research costs doubt upon the validity of Burt's work. (SL)

Results of twin studies clearly demonstrate that genetic factors play an important role in the rate of language acquisition and linguistic proficiency attained by normal and impaired children and adults [see Stromswold, K. (2001). The heritability of language: A review and meta-analysis of twin, adoption and linkage studies. "Language," 77,…

Four studies investigated children's explanations for family resemblance and species-typical characteristics, under different conditions of biological parentage and rearing environment. Participating were 226 children between 3 and 11 years. Children Children were presented with a number of different tasks, some involving people and some domestic…

The modern history of biology shows how Darwin's selectionist theory has replaced instructionist theories in explaining the operations of living things: first with inheritance through the gene pool of the 1850s, and second with the replacement of a template theory of immune system function in the 1960s. Today scholars in several disciplines…

Summary scores for behaviors rated on Bayley's Infant Behavior Record were obtained by summing sequential ratings for same-sex twins participating in a longitudinal study. Composite scores were calculated for two behavioral clusters - one composed of behaviors related to primary cognitions and the other of behaviors related to extraversion.…

Five experiments investigated children's intuitions about genetic transmission of features. Results suggest young children have principled, specifically biological notions of inheritance. (PCB)

The home environment of nonadoptive and adoptive sibling pairs was assessed using the Home Observation for Measurement of the Environment when each sibling was one and two years of age. Correlations between home environment scores for nonadoptive siblings were greater than those for adoptive siblings. (BC)

Describes a methodology of behavior genetics in the context of twin and sibling/adoption design. This model was applied to cross-sectional data on cognitive development throughout the lifespan. Results from a twin and adoption study of general intelligence are presented to illustrate the use of the basic behavior genetic model in studying causes…

Investigated genetic change and continuity within the domains of temperament, emotion, and cognition and language for 200 pairs of twins assessed at 14 and 20 months of age. Correlations of measures at the two ages indicated that individual differences in the second year of life showed greater change than continuity on most measures. (MDM)

This study examining children's understanding of biological inheritance addressed four central questions: (1) are young children able to distinguish between the relative influences of nature and nurture in their understanding of how physical characteristics versus behaviors and preferences develop in animals? (2) does children's understanding of…

The portions of Inequality: A Reassessment of the Effect of Family and Schooling in America (Jencks, et al 1972) concerned with inequality in cognitive skills and estimating the heritability of IQ scores are reviewed. For related articles see TM 501 196-200. (MLP)

In investigations of decline of intellectual status with age, cross-sectional and longitudinal studies give divergent results--the former show almost universal declines in test performances among older groups while the latter often show gains. Although few structure-of-intellect (SI) factors have been explored in relation to adult ages, two kinds…

The purpose of this paper is to clarify some of the conceptual issues involved in discussions of psychology and education which rely on the assumption that biological factors serve as a basis or are responsible for human intelligence. (Author/ND)