This paper demonstrates theoretically and experimentally that in first price auctions overbidding with respect to the risk neutral Nash equilibrium might be driven from anticipated loser regret (felt when bidders lose at an affordable price). Different information structures are created to elicit regret: bidders know they will learn the winning bid if they lose (loser regret condition); or the second highest bid if they win (winner regret condition); or they will receive no feedback regarding the other bids.