What happens in the brain to determine a behavior one second before that behavior occurs? Answering this question forms one of the longest and most difficult chapters in the book. In it, Sapolsky provides an overview of the basic neuroscience of human behavior, which draws on work spanning the last 100 years of scientific examination of the structure of the brain in both animal and human subjects. This chapter deals primarily with the anatomical layout of the brain, particularly the functions of the Limbic System, Frontal Cortex, and Dopaminergic system.

Though challenging, Sapolsky argues that the brain is the all-important topic in the study of behavior because “the brain is the final common pathway, the conduit that mediates the influences of all the distal factors to be covered in the chapters to come” (22). In other words, if we are looking for a place to unite varied sciences of behavior, we should look at the brain. As such, forms and methods of brain research discussed in this chapter, like fMRI—imaging of active brains to see how they respond to different stimuli—and lesion studies—destruction of parts of (animal) brains to see what functions are lost—will be returned to throughout this book.