Is any awareness necessary for an Ne?

Abstract

The Error-Related Negativity (Ne or ERN) is a reliable electrophysiological index of error processing, which has been found to be independent of whether a subject is aware of an error or not. A large Ne was equally seen after errors that were consciously detected (Aware errors) and those that were not (Unaware errors), compared to a small negativity for correct responses (CRN). This suggests a dissociation between an automatic, preconscious error processing mechanism and subjective evaluation. A common concern regarding this finding is that subjects could have been somewhat aware of their errors, but did not report them due to lack of confidence. Here we tested this possibility directly using a betting paradigm which allowed us to separate occasions in which the subjects were confident of their response and trials in which they were unsure. In a choice reaction time task, subjects directly judged the accuracy of each response (correct or error) and then bet on this judgment using a high, medium, or low amount of money. The bets were used to determine the level of confidence the subjects had of their response. The average across all subjects regardless of confidence (betting) measure replicated the reported finding of an equal Ne for Aware and Unaware errors which was larger than the CRN. However, when Ne measurement was confined to high confidence (high bet) trials in confident subjects, a prominent Ne was seen only for Aware errors, while confident Unaware errors (i.e., error trials on which subjects made high bets that they were correct) elicited a response that did not differ from the CRN elicited by truly correct answers. In contrast, for low confidence trials in unconfident subjects, an intermediate and equal Ne/CRN was elicited by CRN, Aware and Unaware errors. These results provide direct evidence that the Ne is related to error awareness, and suggest the amplitude of the Ne/CRN depends on individual differences in error reporting and confidence.

Keywords: Ne; Pe; confidence; error awareness; error processing; wagering.

Figure 1

The trial procedure and some example trials.

Figure 2

Behavioral results of all 22 participants.

Figure 3

Grand average (N = 22) response-locked ERPs to correct and error responses across all bets at electrode (A) FCz and (B) Pz. The bottom panel shows the scalp topography at the time of (A) the CRN/Ne peak and (B) the Pe.

Figure 4

Effect of confidence on response-locked ERPs at electrodes FCz and Pz, when only high (A) or low (B) bets are averaged.

Figure 5

Proportion of each bet category for each response type for the High and Low Confidence groups.

Figure 6

Effect of confidence on response-locked ERPs at electrodes FCz and Pz. (A) High confidence group (B) Low confidence group. (C) The interaction between Group and Response Type.

Figure A1

Grand average waveforms at FCz of (A) the original response-locked results, (B) the response-locked results after the subtraction of the stimulus-locked ERPs, and (C) the stimulus-locked waveforms. The shaded area in the stimulus-locked waveforms represents the average reaction time ± one standard deviation.

Figure A2

Response-locked grand average waveforms of correct responses of the Low Confidence group. (A) The original results at FCz; (B) the results after the subtraction of the stimulus-locked ERPs at FCz. (C) The original results at Pz; (D) the results after the subtraction of the stimulus-locked ERPs at Pz.