How do genes affect cognitive ability? The talks starts with a brief review of psychometric measurements of intelligence, introducing the idea of a “general factor” or IQ score. The main results concern the stability, validity (predictive power), and heritability of adult IQ. After this, ongoing Genome Wide Association Studies which investigate the genetic basis of intelligence is discussed. Due mainly to the rapidly decreasing cost of sequencing, it is likely that within the next 5-10 years we will identify genes which account for a significant fraction of total IQ variation.