He received his PhD in Mathematics from the Hebrew University in Jerusalem in 1997 under the supervision of Nobel Laureate Robert Aumann. Yossi works mainly in the field of foundations of economic theory. His recent work includes the introduction of games with unawareness and analysis of strategic decision making in the face of unawareness, other recent work concerns with the testing of stochastic predictions in a non-Bayesian, non-parametric, setting. Yossi is an associate editor of the Journal of Economic Theory.