Support for the parieto-frontal integration theory of general intelligence in this open-access PNAS paper, Distributed neural system for general intelligence revealed by lesion mapping:
General intelligence (g) captures the performance variance shared across cognitive tasks and correlates with real-world success. Yet it remains debated whether g reflects the combined performance of brain systems involved in these tasks or draws on specialized systems mediating their interactions. Here we investigated the neural substrates of g in 241 patients with focal brain damage using voxel-based lesion–symptom mapping. A hierarchical factor analysis across multiple cognitive tasks was used to derive a robust measure of g. Statistically significant associations were found between g and damage to a remarkably circumscribed albeit distributed network in frontal and parietal cortex, critically including white matter association tracts and frontopolar cortex. We suggest that general intelligence draws on connections between regions that integrate verbal, visuospatial, working memory, and executive processes.
General intelligence (Spearman’s g) is just about the most controversial topic out there, from Gould’s Mismeasure of Man and The Bell Curve to more recent contributions (for and against). Positive correlation between test results across a range of cognitive tasks suggest something links verbal skills, spatial reasoning and memory (but not face recognition). So the debate is more or less about the status of factor analysis.