Authors emphasizing primary mental abilities (Thurstone) or a general ability (Spearman) are reconciled in this hierarchical model, in which g binds together more basic groups of ability, which in turn contain more specific lower-level abilities. Cognitive ability and the volume and connectivity of the central nervous system are related, according to imaging studies. Ability develops throughout childhood, and stimulation from early childhood onward, especially in the form of school-type activities, appears to be the major influence on the development of ability. Programmes for raising intelligence have had little lasting effect, but for children in deprived environments, full-time care and stimulation throughout the years may have a lasting positive effect. Large rises in intelligence test scores in the latter half of the last century may demonstrate the effects of improved physical environment (reduced infection, improved nutrition), increased exposure to education, or even increased practice at school of puzzle-like thinking. Estimates of the heritability of intelligence average around .5, with lower values in the very young, and higher values in older subjects. Specific genes underlying this heritable pattern are being investigated. IQ scores are amongst the most stable measures we have of a person over time. Behavioural genetic research indicates that family environment matters rather little after school begins, but also that family SES is an important constraint on whether genetic talent is expressed - at least within the United States. Intelligence tests yield reliable mean and variance differences between groups, but the causes of these differences remain obscure. Further reading Deary, I. J. (2012). Intelligence. Annual Review of Psychology, 63, 453-482. doi: 10.1146/annurev-psych-120710-100353
Authors emphasizing primary mental abilities (Thurstone) or a general ability (Spearman) are reconciled in this hierarchical model, in which g binds together more basic groups of ability, which in turn contain more specific lower-level abilities. Cognitive ability and the volume and connectivity of the central nervous system are related, according to imaging studies. Ability develops throughout childhood, and stimulation from early childhood onward, especially in the form of school-type activities, appears to be the major influence on the development of ability. Programmes for raising intelligence have had little lasting effect, but for children in deprived environments, full-time care and stimulation throughout the years may have a lasting positive effect. Large rises in intelligence test scores in the latter half of the last century may demonstrate the effects of improved physical environment (reduced infection, improved nutrition), increased exposure to education, or even increased practice at school of puzzle-like thinking. Estimates of the heritability of intelligence average around .5, with lower values in the very young, and higher values in older subjects. Specific genes underlying this heritable pattern are being investigated. IQ scores are amongst the most stable measures we have of a person over time. Behavioural genetic research indicates that family environment matters rather little after school begins, but also that family SES is an important constraint on whether genetic talent is expressed - at least within the United States. Intelligence tests yield reliable mean and variance differences between groups, but the causes of these differences remain obscure. Further reading Deary, I. J. (2012). Intelligence. Annual Review of Psychology, 63, 453-482. doi: 10.1146/annurev-psych-120710-100353
IQ%20chapter%202014.docx