Toward a Molecular Biology of Human Intelligence: Psychometrics Meets Gene Expressions and Brain Metabolism

The ultimate goal of human intelligence research is to increase general intelligence ( g ) in individuals. Here we focus on the potential for molecular biology to help achieve this goal based on specific findings from evolutionary biology, genetics, cognitive neuroscience, and neuroimaging. Our review discusses an evolutionary perspective about why brain metabolism and energy use may underlie human intelligence differences. We include: 1) a role for Human Accelerated Regions (HARs) in the genome, 2) relevant neural networks identified with neuroimaging where the precuneus may be key, 3) specific genes and their expressions that suggest possible causal mechanisms on a molecular level, 4) what polygenic scores contribute to understanding causal mechanisms, 5) diet influences, especially for Polyunsaturated fatty acids (PUFAs), Docosahexaenoic acid (DHA), and other metabolic variables, 6) a possible role for mitochondria and 7) interactions of molecular influences with social/cultural influences. Overall, the findings we review support the proposition that individual differences in intelligence in the population reflect the tradeoff between the energy demands of our recently evolved brains and the metabolic systems that support them. Understanding how these brain systems work can form a basis for molecular studies of human intelligence similar to those of learning and memory. Such studies must be collaborative efforts that build on well-replicated psychometric findings and expand intelligence research even deeper into the brain.