False external feedback modulates posterror slowing and the f-P300: implications for theories of posterror adjustment.

People tend to slow down after mistakes. This posterror slowing (PES) has commonly been explained by a change to a more conservative response threshold to avoid future errors. Alternatively, the attention-orienting account posits that all infrequent, surprising events (including errors) elicit an orienting response followed by a time-consuming process of task reorientation, explaining PES without increased response caution. In the present study, we employed both behavioral and electrophysiological measures to compare the predictions of these accounts using a flanker paradigm in which accurate or false external response feedback was provided. Participants demonstrated typical posterror adjustments, responding more slowly and accurately in posterror than in postcorrect trials. This finding provides initial evidence suggesting that posterror adjustments are motivated by the avoidance of subsequent mistakes. Most importantly, PES and an event-related potential relating to the attentional processing of feedback, the feedback-related P300 (f-P300), were modulated by feedback type. More specifically, the f-P300 was larger after false than after accurate feedback, suggesting that participants oriented their attention toward (i.e., were surprised by) inaccurate feedback signals. Interestingly, false feedback differentially modulated reaction times: Participants were slower after correct responses when feedback falsely informed of an error rather than confirmed the correct response. In contrast, faster responses were made after errors when feedback falsely indicated correct rather than incorrect performance. When these patterns of results are regarded together, they are best explained by theories of cognitive control in which posterror adjustments in choice reaction time tasks are assumed to reflect control processes leading to more conservative performance after error signals.