Fig. 1.

Schematic illustration of the signal detection task (PRT). First, all participants were required to focus on the fixation in the center of the screen (500 ms) followed by a mouthless cartoon face (500 ms). Target stimulus (a short or long mouth) appeared in 100 ms and participants were asked to press the button using their left or right fingers to indicate a short or long mouth. Feedback was provided to the participants for 1750 ms to inform whether they correctly responded to the target and how many tokens were awarded