Roger Ratcliff, Marios G. Philiastide, and Paul Sajda DDRM 4/19/09 Quality of evidence for perceptual decision making is indexed by trial-to-trial variability of the EEG Roger Ratcliff, Marios G. Philiastide, and Paul Sajda

Face/car discrimination task

early late

Is there a relationship at the single-trial level? goal Model fit uses % correct in RT quantiles ([0.1:0.2:0.9]), so cannot be fit on a trial-to-trial basis. => to look at trial-to-trial relationship between model and behavior, here single-trial EEG data is used. Is there a relationship at the single-trial level? model EEG behavior

logic EEG component amplitude was used to divide trials into those with high and low drift rate. Then the model was fit separately to the 2 groups of trials. The fit uses the behavioral results of the sorted trials to extract drift rate. Main result: the drift rate was higher on trials with higher EEG

< Trials of stimulus condition One subject RT, % correct Fit model Fit model ? < Drift rate Drift rate

simulation