General intelligence in the age of neuroimaging

International differences in the speed of cognitive development: A systematic examination of the existence of the Simber Effect

The Simber Effect refers to the phenomenon whereby, in Arabic countries, young children have an IQ that is little different from that of Western children but that these differences increase throughout childhood culminating in a difference of around 20 points by adulthood. The true nature of this phenomenon is revealed by an examination of 125 samples from all around the globe measured with Raven's Progressive Matrices. We show that in many cases different speeds of cognitive development increase the IQ score differences between countries mostly between 4 and 9 years of age, and that these increases can in part be explained by poor environmental conditions. However, the patterns are not completely clear, either in terms of regularity or strengths. Methodological problems, in particular the cross-sectional designs of the included samples, as well as the significance of the Simber Effect for country comparisons in intelligence are discussed.

The Search for the Elusive Basic Processes Underlying Human Intelligence: Historical and Contemporary Perspectives

This article discusses the issues of the basic processes underlying intelligence, considering both historical and contemporary perspectives. The attempt to elucidate basic processes has had, at best, mixed success. There are some problems with pinpointing the underlying basic processes of intelligence, both in theory and as tested, such as what constitutes a basic process, what constitutes intelligence, and whether the processes, basic or not, are the same across time and space (cultural contexts). Nevertheless, the search for basic processes has elucidated phenomena of intelligence that the field would have been hard-pressed to elucidate in any other way. Intelligence cannot be fully understood through any one conceptual or methodological approach. A comprehensive understanding of intelligence requires the converging operations of a variety of approaches to it.