When I entered the field of psychology forty years ago, the dominant paradigm was Skinnerian behaviorism: describe human or animal behaviors as observed, and increase or decrease them through rewards or punishment. The ‘cognitive revolution’ was a major innovation: researchers peered inside the black box and, through theoretical models and experimental interventions, attempted to describe the mental structures and processes that are - or give rise to - thoughts as well as behaviours. Recently, an equally major innovation has been the various forms of brain imaging. Now, in addition to looking into the black box of the mind, we can begin to ascertain the brain processes that undergird cognition and behavior. Next will be the genes that give rise to brain, mind, and behavior - but we will continue to need explanations at all three levels of analysis.

Howard Garner is John H. and Elisabeth A. Hobbs professor of cognition and education at the Harvard Graduate School of Education. adjunct professor of psychology at Harvard University and senior director of Harvard Project Zero.