He studies fundamental questions of population behavior and decision-making, with a focus on how how integrating behavioral evidence into policies can reduce inequalities and improve population well-being.

His recent projects involve behavioral policy studies focusing on large-scale data related to economic choices and related outcomes, which have been covered in media around the world. Collaborating partners include local and national governments, non-profit organizations, industry, and other academic institutions, in New York, various parts of the US, and abroad. Kai joined Columbia from the Department of Psychology at the University of Cambridge, where he directed the Policy Research Group that he founded in 2013.