stimulus. Response-locked ERP epochs spanned from 200 ms before to 600 ms following the response. To improve the visual presentation of the data, all epoched waveforms were then band-pass-filtered using a zero phase shift FIR filter between 1 and 12 Hz. The first half of the pre-stimulus interval served as baseline for the stimulus-locked potentials (−400 to −200 ms) while the response-locked potentials were baseline-corrected using the first half of the pre-response interval (−200 to −100 ms). All of the fronto-central potentials (N2, CRN, and ERN) were examined at electrode FCZ because that is the topographical location where the peaks reach maximum negative amplitude. The N2 and CRN amplitudes are given for each correct trial condition type (HsHr, HsLr, LsHr, LsLr). ERN values reflect the average of incorrect responses across these four conditions because too few trials were available to produce a reliable waveform for each condition. The time interval in which the average or peak values were extracted were determined by both published results and visual inspection of the individual waveforms. These intervals are specified for each potential in their respective results section.
