This book’s premise rests on the work of psychologists Dean Keith Simonton and Raymond Cattell. Simonton’s research into creative productivity and career trajectories forms the basis of Chapter 1—the crux of Brooks’s argument that mental decline is so widespread and predictable that it is inescapable.

Simonton based his conclusions on two decades of research into scholarly and creative careers—that is, careers stemming from the mind. He examined various creative disciplines and noted each individual’s first contribution to the field, as well as that person’s best contribution—representing peak performance—and final contribution. One graph showed the results for nine different subjects in math and the sciences (Simonton, Dean Keith. “Creative Productivity: A Predictive and Explanatory Model of Career Trajectories and Landmarks.” Psychological Review, vol. 104, no. 1, 1997, p. 75).

Another graph compared the results of different disciplines, including sciences and the arts (Simonton, Dean Keith 71). The graphs were remarkably similar: All individuals showed peak performance roughly 20 years into a career, no matter when the career began or which field it was in.

Simonton holds a PhD from Harvard University and is Distinguished Professor Emeritus of Psychology at the University of California, Davis. His work has focused on creativity, leadership, and intelligence.