What do research psychologists do? How do they think about their work? What does psychological science look like as it goes on in the heads of top psychological scientists? How do these scientists develop their ideas over time?

The purpose of this book is to hear, in the first person, from some of the most eminent psychologists of the modern era regarding what they view as their single most important contribution to the behavioral and brain sciences. The list of invitees was based on rankings compiled by Diener, Shigehiro, and Park (2014), using criteria such as number of major awards, total number of citations, and pages of textbooks devoted to the scholars’ work. Such lists, of course, would have different members depending on the criteria used, but the list seemed to us as good a basis for recognition as any we could find.

We invited all living members of the list of 200 individuals (many were deceased at the time we were preparing the book) for whom we could find contact information. The overwhelming majority of individuals still living and able to write, 100 scientists in all, agreed to write either singly or jointly, yielding 101 chapters, including the introduction and conclusion. (Some individuals were still alive but no longer in sufficiently good health to be able to write a chapter.) In each case, they were given the option of either writing a sole-authored piece (which the large majority did), writing with another member of the list (which happened in two cases, in which the individuals became famous for their collaborative work), or writing with someone outside the list (which happened in one case, in which the junior author of the chapter was instrumental to the accomplishment of the work described). After asking each member of the list to write, we asked two additional extremely distinguished psychologists who are also academic leaders and administrators – a university president and a university chancellor – to write the foreword and afterword, and both agreed to do so.

Each essay addresses just five questions:

1. 1. What do you consider to be your most important scientific contribution?

2. 2. Why do you consider it to be your most important contribution?