Abstract:

Previous studies have suggested that some cognitive control functions such as inhibition control and task switching were independent of consciousness, but it is unclear whether consciousness is necessary for conflict adaptation. Prior studies in consciousness domain showed that conflict adaptation reflected on behavioral measures and ERP components (N2 and P3). The purpose of current study is to test whether consciousness is necessary for conflict control. If conflict control was independent of consciousness, we would observe that the conflict effect indexed on reaction times and N2 and P3 amplitude modulated by previous trial congruency regardless of consciousness. If these hypotheses were verified, it could deepen our understanding of unconscious information processing and give us insight into the function of consciousness. To test our hypotheses, we obtained the behavioral and electroencephalogram (EEG) data from 18 subjects using an arrow version meta-contrast masking task, in which the primes fitted exactly within the inner contour of the target. By manipulating the time interval of prime and target and the presentation time of primes, the prime can be weakly or strongly masked. One subject was excluded from further analysis due to too many artifacts. To exclude the alternative interpretation of conflict adaptation by stimulus/response repetitions, stimulus or (and) response repetitions trials were removed before further analysis. After removing the artifacts included in the EEG segments, the ERPs were obtained according to each condition. The negative peak of N2 was averaged during 240-320 ms across fronto-central ROI electrode sites, while the P3 was averaged during the time 350-500 ms across centro-parietal ROI electrode sites. All analyses were performed separately based on the conditions of consciousness. The results showed that there was reliable conflict effect on reaction times and N2 and P3 amplitudes under conscious and unconscious conditions, and these effects were modulated by the congruency of previous trial type. Specifically, the conflict effect is smaller when the previous trials were incongruent than when they were congruent. Nevertheless, the size of conflict adaptation effect indexed on reaction times and N2 amplitude were larger under conscious condition than under unconscious condition, while the size of conflict adaptation between conscious and unconscious conditions were not significant. To our knowledge, we are the first to use ERP methods to study whether consciousness is necessary for conflict adaptation. These results not only suggest that the unconscious experience has great impact on human information processing system, but also suggest that conflict control is independent of consciousness. The difference in magnitude of conflict adaptation effect may come from the magnitude difference of conflict effect, and conscious conflict is far larger than unconscious conflict. Thus, in further studies we should pay attention to the difference and common aspects on unconscious and conscious conflict control. Moreover, the conflict monitoring theory can be perfectly interpreted the conflict control, but it do not elucidate the function of consciousness in the loop of conflict control. In conclusion, the current findings indicate that conflict adaptation is independent of consciousness. The current study could give some insights to understand and reveal the function of consciousness as well as its effect on conflict control.

Key words: conflict adaptation, unconscious, conscious, conflict control, event-related potentials (ERPs)