P3 and Stimulus Incentive Value

Event‐related potentials were recorded to two equiprobable, task‐relevant visual stimuli (0.00 and 1.00) under three different conditions. In the baseline condition subjects attended to both stimuli and pressed the appropriate button to each stimulus. In the Accuracy/Incentive condition subjects earned one dollar each time the 1.00 stimulus was presented by accurately pressing the appropriate button after each stimulus. Incorrect presses to either stimulus resulted in the loss of a dollar. In the Speed‐Accuracy/Incentive run, subjects could only earn one dollar to the 1.00 stimulus if they accurately pressed the correct button within 350 msec. Reaction times greater than 350 msec to either stimulus resulted in the loss of a dollar. The results indicate that the amplitude of the P3 component is significantly different to equiprobable task‐relevant stimuli with differential incentive values. P3 may reflect the subjective motivational properties of stimuli.