The brain's orbitofrontal cortex deals with social interactions, including regret, and has been much studied with fMRI and EEG. Using ECoG, which provides more detailed information about brain activity on millisecond timescales and with better resolution, researchers were able to follow the thoughts that swirl through this brain area during a simple betting game. Surprisingly, after placing a bet, gamblers dwell mostly on regret over previous bets, whether won or lost, essentially second-guessing previous decisions.