Figure 2. Schematic Representation of a Single Trial of the Value Learning Task in the Face and Fractal Conditions.

A and B, In the baseline trials, a pair of static stimuli (faces in the face condition and fractals in the fractal condition) is presented in 2 of 4 randomly selected locations. Baseline consists of 4 trials. Each of the baseline trials began with a presentation of a central fixation point for 600 milliseconds (ms). The offset of the central fixation point coincided with the presentation onset of the pair of stimuli (faces or fractals) lasting for 4000 ms. A gray screen was presented during each intertrial interval lasting randomly between 400 and 800 ms. In the training trials, during a high-value (HV) trial (shown), the fixation (marked as an upright arrow) on an HV object results in the activation of a dynamic display (smiling face or revolving fractal). During a low-value (LV) object trial (not shown), fixation on the LV object results in no change to its display. Training consists of 48 trials. Each trial started with the presentation of a central fixation point (multicolor pulsating circle) for 600 ms, followed by the presentation of either the HV or LV stimulus in 1 of 4 randomly selected locations for 2000 ms. There was a 300-ms overlap between the presentation of the central fixation point and the stimulus to diminish the likelihood that participants would look away from the screen before the onset of the peripheral stimulus. In the choice test trials, a pair of static stimuli is shown in 2 of 4 randomly selected locations. Choice test consists of 6 trials, where locations of the HV and LV objects are randomized, with the same structure as the baseline trials.