Here, intelligence is taken to mean scores from psychometric tests of cognitive functions. This essay describes how cognitive tests offer assessments of brain functioning--an otherwise difficult-to-assess organ--that have proved enduringly useful in the field of health and medicine. The two "consequential world problems" (the phrase used…

Most study samples show less variability in key variables than do their source populations due most often to indirect selection into study participation associated with a wide range of personal and circumstantial characteristics. Formulas exist to correct the distortions of population-level correlations created. Formula accuracy has been tested…

Previous research has indicated that education influences cognitive development, but it is unclear what, precisely, is being improved. Here, we tested whether education is associated with cognitive test score improvements via domain-general effects on general cognitive ability ("g"), or via domain-specific effects on particular cognitive…

Three hundred and four participants in the Lothian Birth Cohort 1936 study took a validated IQ-type test at age 11 years and a battery of cognitive tests at age 70 years. Three tests of health literacy were completed at age 72 years; the Rapid Estimate of Adult Literacy in Medicine (REALM), the Test of Functional Health Literacy in Adults…

This study investigated the possibility that apparent sex differences in IQ are at least partly created by the degree of sample restriction from the baseline population. We used a nationally representative sample, the 1970 British Cohort Study. Sample sizes varied from 6518 to 11,389 between data-collection sweeps. Principal components analysis of…

There is a significant association between birth weight and cognitive test scores in childhood, even among individuals born at term and with normal birth weight. The association is not explained by the child's social background. Here we examine whether mother's cognitive ability accounts for the birth weight-cognitive ability association. We…

Individual differences in cognitive ability may in part have prenatal origins. In high-risk (low birth weight/premature) babies, birth weight correlates positively with cognitive test scores in childhood, but it is unclear whether this holds for those with birth weights in the normal range. The authors systematically reviewed literature on the…

Change in cognitive functioning is an important aspect of human aging and a key outcome in many medical conditions. However, cognitive change can rarely be measured directly, since prior cognitive data do not exist for most people. We examined the criterion validity and one-year stability of the difference between National Adult Reading Test…