12 Understanding Human Intelligence by Imaging the Brain Roberto Colom and Paul M. Thompson This chapter reviews the biological basis of individual differences in human intelli- gence. However, we note from the outset that our review is based on results derived from the application of neuroimaging methods. Both structural and functional approaches are considered here. The first section discusses what we call “the brain connection,” a phrase which designates the fact that genetic and non-genetic factors influencing intelligence play on the brain. Understanding this psychological factor requires deep knowledge regarding brain structure and function. Secondly, intelli- gence is defined and some implications are derived from the standardized measure- ment of this construct. The distinction among “constructs,” “vehicles,” and “measurements” is especially relevant in this context. The section on methods presents the main structural and functional approaches employed so far for analyzing the intelligence construct. Neuroimaging studies involve creating models and maps of the brain. Typical data are cortical thickness, gray matter density, gyral pattern variability, hemispheric asymmetry, heritability, or fMRI signals. It is highlighted that the study of white matter is developing quickly and provides useful insights. The next section discusses key findings within the framework defined by the parieto-frontal integration theory of intelligence (P–FIT, Jung & Haier, 2007). Interestingly, it is shown that this theory is also relevant for other psychological constructs, like working memory capacity or attention. This overlap underscores frontal and parietal brain areas, along with their connections, for understanding individual differences in cognition. The chapter ends by suggesting a movement from correlation to experimental approaches for studying the biological base of intelligence by means of techniques such as TMS (transcranial magnetic stimulation). The Wiley-Blackwell Handbook of Individual Differences, First Edition. Edited by Tomas Chamorro-Premuzic, Sophie von Stumm, and Adrian Furnham. © 2011 Blackwell Publishing Ltd. Published 2011 by Blackwell Publishing Ltd.