August 23, 2026, marks ten years since the passing of Reinhard Selten. A pioneering game theorist and Nobel laureate, Selten fundamentally reshaped how we think about strategic interaction and decision-making. His influence lives on through his research and the many scholars he mentored.
To honor his legacy, we are launching a series of interviews with Reinhard Selten’s former students, colleagues, and close associates. They share personal memories and reflect on his enduring influence on economics. Our Interview series begins with Bernd Irlenbusch, Professor at the University of Cologne’s Department of Management.
In your view, what was Reinhard Selten’s most important scientific contribution, and how would you explain it in simple, non-technical terms?
If I had to single out one contribution, I would choose Selten’s development of subgame-perfect equilibrium, which fundamentally sharpened our understanding of strategic behavior. In simple terms, he showed that a strategy is only really convincing if it remains sensible at every point at which a decision might actually have to be made—so that, for example, an empty threat cannot determine what we expect people to do.
At the same time, Selten was a pioneering experimentalist because he took seriously what people actually do rather than dismissing behavior simply because it does not conform to an elegant theory. He described himself as a “methodological dualist”: someone who approached economic behavior both through formal mathematical theory and through experiments designed to understand actual human behavior. To me, this combination of theoretical rigor and empirical openness is one of the most distinctive and enduring features of his scientific legacy.
The Reinhard Selten Institute takes particular pride in supporting researchers at the beginning of their careers. Is there any piece of advice or insight from Reinhard Selten that you would like to share with them?
One lesson I associate very strongly with Reinhard Selten is not to be afraid of questions that lie outside the mainstream. He was extraordinarily rigorous, but at the same time willing to enter largely unexplored territory.
Is there a personal anecdote or memory of Reinhard Selten that you remember particularly fondly?
One memory that has stayed with me goes back to my time as a PhD student. We had to present our work in a faculty seminar that was rather feared by young researchers, and it was considered very advisable to choose a date when Reinhard Selten could attend. He had the intellectual authority—and the instinct—to step in when the discussion became a little overwhelming.
I vividly remember my own seminar in which, as often happens with experimental work, members of the audience came up with numerous suggestions for additional treatments that supposedly ought to be run. At some point, Selten intervened and said, in essence: “If you think it is important to run such a treatment, you should do it yourself.” That immediately changed the atmosphere in the room. As a PhD student, you could hardly have wished for stronger backing from your supervisor. It was a wonderful example of how Selten combined scientific rigor with loyalty to and protection of young researchers.