Recent research strengthens the conjecture that human decision-making stems from a complex interaction of rational judgment and emotional processes. A prominent example of the impact of emotions in economic decision-making is the effect of regret-related information feedback on bidding behaviour in first-price sealed-bid auctions. Revealing the information “missed opportunity to win” upon losing an auction, results in higher bids. Revealing the information “money left on the table” upon winning an auction, results in lower bids. The common explanation for this pattern is winner and loser regret. However, this explanation is still hypothetical and little is known about the actual emotional processes that underlie this phenomenon. This paper investigates actual emotional processes in auctions with varying feedback information. Thereby, we provide an approach that combines an auction experiment with psychophysiological measures which indicate emotional involvement. Our economic results are in line with those of previous studies. Moreover, we can show that loser regret results in a stronger emotional response than winner regret. Remarkably, loser regret is strong for high values of “missed opportunity.” However, the pattern for different amounts of “money left on the table” is diametric to what winner regret theory suggests.