On the correct side of performance: Processing of internal and external signals in response speed evaluation.

Response appropriateness is not exclusively limited to accuracy. Nevertheless, the processing of parameters other than accuracy for response monitoring has been mostly neglected. The present experiment explored how the cognitive system processes response speed based on internal and external signals. Participants performed a response-choice task where correct responses were classified as fast, average, or slow. External signals informative about performance quality were presented after the response in most of the trials; in some trials, instead, participants had to judge their own performance. Event-related brain potentials (ERPs) of response and feedback processing were analysed to investigate how the cognitive system monitors correct responses. Response quality affected the processing of internal signals. That is, both the response-related negativity (correct-related negativity, CRN) and positivity (correct positivity, Pc) showed modulations related to speed: with the largest and the smallest amplitudes associated with fast and slow responses, respectively. We ascribe these modulations to positive arousal associated with the optimal nature of correct fast responses. Response quality, also affected feedback processing. Here, response speed significantly modulated the feedback-related negativity (FRN) and had an effect on the latency and the magnitude of the preceding positive peak. These effects in feedback processing seem related to feedback expectation in a context where awareness of feedback quality is vague and average performance, although more difficult to detected, is generally expected.