When Byrne wrote "In Particular," she had the benefit of a very rich century's worth of research on human consciousness and intelligence. The twentieth century witnessed a huge leap forward in the understanding of the human brain, thanks in part to the introduction of psychoanalysis, a method that sought to investigate disorders of the mind. Psychoanalysts such as Sigmund Freud, one of the early psychoanalytic theorists and practitioners, believed that these disorders were caused by conflict between the conscious mind and repressed forces that resided in a person's unconscious mind. The way to treat these disorders, psychoanalysts believed, was to use dream analysis, free association, and other mental tools to try to discover these problematic, repressed forces and work through their underlying causes. But until the late twentieth century, when biomedical science also made a huge leap forward, psychoanalysis relied largely on theory to support its...