On the locus of the effect of alerting on response conflict : an event-related EEG study with a speed-accuracy tradeoff manipulation

The present study investigated the locus of the effect of alerting on response conflict, and examined whether this effect may be interpreted as an alerting-triggered imbalance of speed-accuracy tradeoff (SAT). Participants performed the flanker task with an alerting tone in half of the trials and SAT manipulation. Behavioral results showed the usual increase of the conflict effect (incongruent-congruent flankers) in the alerting trials. This interaction was not affected by SAT manipulation in response times, although accuracy emphasis abolished alerting effects in error rates. Event-related potential (ERP) results showed that alerting increased the conflict by facilitating the selection and activation of stimulus-response links, reflected in modulations of the P3b component, and by enhancing the activation of incorrect response evoked by incongruent flankers, reflected in an increased initial incorrect activation in the lateralized readiness potential (LRP). Time-frequency analysis showed that the alerting-triggered increase of conflict entailed stronger response of executive mechanisms, reflected in a larger conflict-related midfrontal theta-band power. These EEG effects were not affected by SAT manipulation. In conclusion, alerting affects both the emergence of conflict and conflict control, and this alerting-conflict interaction could not be explained in terms of SAT