Probability Learning and the P3 Component of the Visual Evoked Potential in Man

Evoked potentials were recorded to stimuli (S1) which were predictive of stimuli (S2) worth different monetary values to determine if these waveforms reflected the probability and/or the value of the predicted event as the subject learned the relationship between S1 and S2. Both the monetary value of S2 and its conditional probability following S1 were systematically manipulated over a wide range of values. Subjects were required to use the conditional probability information (0.5,0.75,1.0) in order to make a correct behavioral response and receive the monetary payoff ($0, $1, $2). The results indicate that the amplitude of the P3 component of the average evoked response to S1 increases as subjects learn the relationship between S1 and S2, and S2 is a high value event.