outcomes were equal), although the participants were not aware of this information. However, since the subject has the option to freely select the amount during each trial, the relative probability for each of the four outcomes (+50, −50, +10, −10) ranged from 0 to 50%. For example, if a subject selects ‘50’ in all the trials, the probabilities will be 50%, 50%, 0%, and 0% for the outcomes of +50, −50, +10, −10, respectively. Trial epochs containing the outcome stimuli (1000 ms poststimulus) representing the feedback of either loss or gain for each trial (i.e., the epochs following colored frames in Fig 1) were used for ERO signal processing. A prestimulus interval of 200 ms prior to the OS was used for the ERP/ERO preprocessing and/or analyses. The trials were presented in two equal size blocks, and the subjects were given a feedback of the cumulative amount lost or gained at the end of each block. At the end of the experiment, participants were paid a constant amount (irrespective of their net loss or gain) for their participation.
