Individual differences in mismatch negativity measures of involuntary attention shift

Objective: The purpose of this study was to compare the automatic detection of deviance in introverts and extraverts. Event-related potentials were re corded to standard and deviant stimuli. These were presented either rapidly or slowly. Stimuli that are presented slowly may intrude into consciousnes s. Methods: Twenty subjects were tested and divided into introverted acid extr averted groups. A 500 Hz standard stimulus was presented on 85% of trials. On the remaining 15% of trials, a 750 Hz deviant was presented. In separate conditions, stimuli were presented rapidly (every 500 ms) or slowly (every 1500 ms). Subjects ignored the stimuli while reading. Results: The deviant stimulus elicited a mismatch negativity (MMN) in both conditions, No inter-group differences in the MMN emerged when a rapid rate of presentation was employed. When a slower rate was employed, a late nega tivity was significantly larger for the extraverted than the introverted gr oup. This was followed by a late positive wave. Conclusion: The late negative-positive complex is thought to reflect intrus iveness. It would therefore appear that extraverts are more distractible th an introverts when stimuli are presented slowly. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.