The Standard Progressive Matrices (SPM) was administered to a sample of 592 16 year old school students in Libya. There was a small negative correlation of -0.14 between SPM scores and the number of siblings, indicating only marginal dysgenic fertility. Supplementary material giving the data is given online. (Contains 1 table.)

Research utilizing individual-level data has reported a link between intelligence (IQ) scores and health problems, including early mortality risk. A growing body of evidence has found similar associations at higher levels of aggregation such as the state- and national-level. At the same time, individual-level research has suggested the…

Using more complex items than those commonly employed within the information-processing approach, but still easier than those used in intelligence tests, this study analyzed how the association between processing speed and accuracy level changes as the difficulty of the items increases. The study involved measuring cognitive ability using Raven's…

We recently proposed the Creative Reasoning Test (CRT), a test for reasoning in ill-defined problem spaces. The test asks children who first performed the Standard Progressive Matrices test (SPM) to next generate an SPM-style test item themselves. The item is scored based on different aspects of its complexity. Here we introduce a method to…

Child prodigies are unusual for their early and exceptional adoption of what are traditionally thought of as adult abilities. As part of an effort to better understand the underpinnings of these extraordinary individuals' talent, the researcher examined the cognitive and developmental profiles of eight child prodigies by taking their developmental…

An impressive body of research has revealed that individual-level IQ scores are negatively associated with criminal and delinquent involvement. Recently, this line of research has been extended to show that state-level IQ scores are associated with state-level crime rates. The current study uses this literature as a springboard to examine the…

Research has consistently revealed that average IQ scores vary significantly across macro-level units, such as states and nations. The reason for this variation in IQ, however, has remained at the center of much controversy. One of the more provocative explanations is that IQ across macro-level units is the result of genetic differences, but…

The Minnesota Study of Twins Reared Apart (MISTRA) was initiated in 1979 and continued until 2000. It consisted of 139 pairs of twins who had been separated in early childhood and not re-united until adulthood, and members of their families. As part of a broader assessment, these participants completed 42 mental ability tests from three well-known…

Childhood intelligence (age 11) and occupational social status at midlife (age 46 to 51) was associated with marital status and reproduction in a sample from the Aberdeen Children of the 1950s cohort study (N = 9614). Male and female divorcees had lower childhood intelligence test scores than their married counterparts, but no meaningful…

The general differentiation hypothesis states that the strength of the correlations among a set of IQ subtests varies with a given variable. Instances of the general differentiation hypothesis that have been considered in the literature include age and ability differentiation. Traditionally, the differentiation effect is attributed to the varying…

The ranking of Wechsler subtests in terms of their "g" loadings is equivalent to ranking them in terms of the cognitive complexity of the tasks measured. Lower performing groups do not always fall behind higher performing groups the more complex the task. But that is the general rule, no matter whether the cause of the lower performance…

The acknowledged high relationship between working memory and intelligence suggests common underlying cognitive mechanisms and, perhaps, shared biological substrates. If this is the case, improvement in working memory by repeated exposure to challenging span tasks might be reflected in increased intelligence scores. Here we report a study in which…

Item responses to Digit Span and Letter-Number Sequencing were analyzed to develop a better-refined model of the two working memory tasks using the finite mixture (FM) modeling method. Models with ordinal latent traits were found to better account for the independent sources of the variability in the tasks than those with continuous traits, and…

To understand the extent to which the general-factor loadings of tests are inherent in their characteristics or due to the sampling of tests, the number of tests in the correlation matrix, and the factor-extraction methods used to obtain them, test scores from a large sample of young adults were inserted into independent and overlapping batteries…

Heterogeneous results among neuro-imaging studies using psychometric intelligence measures may result from the variety of tests used. The g-factor may provide a common metric across studies. Here we derived a g-factor from a battery of eight cognitive tests completed by 6929 young adults, 40 of whom also completed structural MRI scans. Regional…