Behavioral approaches rooted in economics and ultimately psychology are making a comeback in international relations. For those with access to the Cambridge Core, a special issue of International Organization edited by me and colleagues Emilie Hafner-Burton, David Lake, and David Victor surveys the field; a more newsy summary can be found here. This work has gone off in a number of different directions, from Elizabeth Saunders on the role of experience to Keren Yarhi-Milo on credibility.
But a group of psychologists and psychiatrists have been taking a different approach: to question the president's fitness for office, and particularly fitness to manage nuclear weapons. This project has now been released as a series of short essays edited by John Gartner called Rocket Man: Nuclear Madness and the Mind of Donald Trump. A Salon summary can be found here.
As a political scientist raised on the effects of strategic and institutional constraints, my contribution to the volume took a somewhat more prosaic view. I considered how Kim Jong Un's race to complete strategic nuclear and missile forces played an important role in forcing subsequent developments; Van Jackson at Politico makes similar points. Since the summit, I have noted that a number of features of the administration's foreign policy were on display in Singapore, including one noted by Keren Yarhi-Milo in particular: that personal chemistry has an upside as well as a downside. On the one hand, it can generate the empathy necessary to see an adversary's point of view and find negotiating space. But too much empathy and personal interests get conflated with national ones, and to the detriment of the latter.