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

DDRM 4/19/09

Face/car discrimination task

early late

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?

modelEEG

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 conditionOne subject

RT, % correct RT, % correct

Fit model Fit model

Drift rate Drift rate?<

sim

ulat

ion