Some of the most intriguing issues in the study of cognitive, social, emotional, and physical development arise in the debate over nature versus nurture; a debate difficult to resolve because it is difficult to separate the respective contributions of genes and environment to development. The most powerful approach to this separation is through longitudinal adoption studies. The Colorado Adoption Project is the only longitudinal adoption study in existence examining development continuously from birth to adolescence, which makes it a unique, powerful, (...) and tremendously valuable resource. CAP is an ongoing assessment of 245 adopted children and 245 biological control children assessed from birth to early adolescence. This book is the fourth in a series describing CAP results. This latest volume, edited by four eminent researchers in developmental psychology, builds on the large body of research already generated by investigating the role of genes and environments on early adolescent development. Because it is the only volume on the most comprehensive investigation of the effect of genes and environments on early adolescent development, this work will be invaluable to researchers in developmental, cognitive, and social psychology. (shrink)

Psychological traits and disorders are often interrelated through shared genetic influences. A combination of maximum-likelihood structural equation modelling and multidimensional scaling enables us to open a window onto the genetic architecture at the symptom level, rather than at the level of latent genetic factors. We illustrate this approach using a study of cognitive abilities involving over 5,000 pairs of twins.

Four questions are raised about Mealey's genetic argument: (1) Where is the evidence that secondary sociopathy is less heritable than primary sociopathy? (2) What is the genetic correlation between the two types of sociopathy? (3) How does genotype-environment interaction relate? (4) How strong are the links between our evolutionary past and current heritability?

Much has been learned about genetic influence on cognitive abilities that might be helpful in thinking about genetic influence on other abilities such as art and sports, which have not yet been investigated using genetic research strategies. Some new findings on cognitive abilities go beyond merely demonstrating genetic influence. Misinterpretations of the meaning of genetic influence are discussed.

Although neither the genome nor the environment can be manipulated in research on human behaviour, some of the new tools of molecular genetics can be brought to bear on human behavioural disorders (e.g. cognitive disabilities) and quantitative traits (e.g. cognitive abilities). The inability to manipulate the human genome experimentally has had the positive effect of focusing attention on naturally occuring genetic variation responsible for behavioural differences among individuals in all their complex multifactorial splendour. Genes in such complex multiple‐gene systems are (...) called quantitative trait loci (QTLs), which merge the two worlds of genetic research, quantitative genetics and molecular genetics. Although most genetic research on complex human behaviour has focused on severe mental disorders, cognitive abilities and disabilities may be even more immediately relevant to neuroscience. For example, verbal ability and spatial ability are two of the most heritable cognitive abilities, and reading disability is the first behavioural disability for which replicated QTL linkage has been found. The purpose of this essay is to provide an overview of the genetics of cognitive abilities and disabilities as an example of the impending merger of quantitative genetics and molecular genetics in QTL analysis of complex traits. (shrink)