CS onset. The OS would not appear if the subject did not respond/select within the specified time (1000 ms), and the next trial would commence. While the occurrence of loss (in red) or gain (in green) in the OS was maintained at equal probability (50%), the order of appearance was pseudo-randomized. The choice was always between 10 and 50 on every trial; 10 always occurred on the left and 50 on the right. The subjects were not made aware of the probability of loss/gain or sequence of the task prior to the experiment. There were a total of 172 trials and the inter-trial interval was 3000 ms throughout the experiment. The task was presented in two blocks with each block (with 86 trials) lasting for 4 minutes; the procedure was identical in both blocks. At the end of each block, the status of overall ‘loss’ or ‘gain’ for the entire block was displayed on the monitor screen. The next block was started by the operator when the subject was ready. At the end of the experiment, all the participants actually received the monetary rewards which they had accrued.
