Experimental procedure.

<p>At the beginning of each trial, a vertical line separating the screen into the left and the right, was presented along with a text ‘Choose’. Participants were required to choose either the left or the right field by pressing the corresponding key within 2 seconds. They were told that the other two participants were also making decisions at the same time. Then, the choice of the participant and the choices of the two confederates in separate rooms were revealed on the screen for 2 seconds. Each individual's choice was indicated by the location of his/her photo and the participant's choice and two confederates' choices were highlighted in different colors. Then they received a “You win” or “You lose” feedback for 2000 ms. The colors (green or red) associated with positive/negative feedback were counterbalanced. The given trial represents an independent-loss condition in which the subject has chosen the right field and loses whereas the two confederates have chosen the left field and won. The subjects of the photographs have given written informed consent, as outlined in the PLOS consent form, to publication of their photographs. The images used in the figure are not the original images used in the study, but similar images used for illustrative purposes only.