Abstract:

Recently, Mai Xiaoqin et al. applied ERPs to examine the electrophysiological correlates of insight by providing a trigger (the solution) to catalyze the insightful riddle solving process. The authors found that Aha answers elicited a more negative ERP deflection (N380) than did No-aha answers in the time window from 250-500 ms. The dipole analysis localized the N380 generator to the ACC. Thus, they argued that the N380 likely reflected an “Aha” effect, and that the ACC generator might be involved in breaking the subject’s mental set. However, the researchers only analyzed the ERP elicited under the conditions of “Aha” and “No-aha” answers, but did not include ERP analyses for the participants that were unable to understand the correct answers (“Uncomprehended answer”). It is known that insight is a complex cognitive process, and there exists doubt whether N380 (the ACC’ activation) would truly reflect the perception of cognitive conflict in the early insight onset. Participants had the Aha experience if they could understand the right answer, but if they could not understand the right answer, they would not have the Aha experience and thus could not obtain insight. Therefore, analyzing the ERP elicited by Unknown answers was important, because it could further clarify the true meaning of N380.
Method
High-density event-related potentials (ERPs) were recorded to examine the electrophysiologic correlates of insight problem solving. One hundred and fifty interesting Chinese logogriphs were adopted as materials. For each trial, participants were either given an easy puzzle followed by a correct answer that was consistent with their initial thinking (No-aha answer), or a difficult puzzle followed by a correct answer that was consistent with an unusual interpretation, so that it broke the participant’s initial mental set (Aha answer). Participants were required to press the corresponding keys to indicate whether they understood the meaning of the riddle, including No-aha answer, Aha answer and Uncomprehended answer. According to participants’ responses, EEG of the “No-aha”, “Aha”, “Uncomprehended” answers was separately overlapped. The averaged epoch for ERP was 800 ms including a 100 ms the pre-answer baseline.
Results
In 130 riddles, mean trials for 61, 44 and 25, SE=5, 6 and 5, for Aha answers, No-aha answers and Uncomprehended answers, respectively. Mean reaction times (RTs) were 2,049 ± 561 ms for Aha answers and 748 ± 289 ms for No-aha answers; other riddles were not answered correctly within 4000 ms. From ERP waveforms, we found Aha answer and Uncomprehended answer both elicited a more negative ERP deflection than did No-aha answer in the time interval between 250-400 ms. In the difference waves (Aha minus No-aha answer and Uncomprehended minus No-aha answer), the peak latency was about 320 ms. A voltage map of the difference wave showed strong activity at the central posterior region, especially at the right temporal parietal. The Dipole analysis (BESA software) localized the generator of the N320 (Aha minus No-aha answer) in near the ACC and the thalamus.
Conclusions
Our results indicated that Aha answer and Uncomprehended answer both elicited a more negative component than did No-aha answers. The N320 may embody the central locale of cognitive conflict that resolves familiar and new ways of thinking, as the participant attempts to comprehend the riddles answers, but do not reflect the breakthrough of the participant’s initial mental set and the temporal course of brain processes corresponding to Aha experience in solving insight problems

Key words: riddle, insight, cognitive conflict, ERP