Abstract: Cognitive insight phenomenon is one of the components of creativity which lies at the core of numerous discoveries. Our developed high spatial resolution brain imaging (e.g. functional magnetic resonance imaging) and excellent temporal resolution event related potentials techniques have made it possible to explore the brain mechanism and neural basis of insight problem solving. Nowadays, neurocognitive mechanism of insight embedded an “Aha” experience is a hot studying but still mystery topic. The present study tries to give an answer.
The present study adopted normal three-word Chinese riddles and employed high-density event related potentials (ERP) to investigate the neural correlate and hemispheric difference involved in insight problem solving. In order to acquire enough reliable and normal three-character riddles, 190 riddles were rated their understanding on a scale of 1 (extremely boring/old) to 5 (extremely interesting/novel) by 103 subjects in the preparatory experiment. About one-half of the 120 riddles were very difficult and the other halves were comparatively easy. It was not easy for participants to work out the solutions to those difficult riddles so that the insight or “Aha!” response and uncomprehended response could be elicited when they were informed the correct answer. And then another nineteen paid participants were recruited in the ERP experiment. Each trial began with a central fixation cross for 500ms, and then blank screen appeared. After 300ms, the three-character question was presented in the center of screen for 7 sec followed by a 300-millisecond interval. Participants were instructed to try to work out the solution to the riddle within this 7.3-sec interval. The possible answer or solution to the riddle was then presented in the center of the screen for 4 sec, followed by a random interval ranging from 200 to 6000ms. Participants were required to press the “1”, “2” or “3” key of number keyboard to indicate whether they had understood the meaning of the riddle. If they understood the riddle answer and their own guesses were consistent to the correct answers, they were asked to press “1” key with their index finger of right hand; if they did not work out the riddle but they could understand the correct answers, they were asked to press “2” key with their middle finger of right hand; if they neither worked out the riddle nor understood the presented answers, they were asked to press “3” key with their ring finger of right hand. Pressing no key as other responses which might include unknown cognitive process were excluded in analysis.
Behavioral data showed that RT to “Aha!” responses and uncomprehended responses significantly larger than RT to No-aha responses. ERP waveform analysis revealed that “Aha!” and uncomprehended responses elicited a more negative defection (N380) than No-aha responses did in 320-550 msec. and exhibit prominent RH effect in “Aha” responses, but there was no significant difference among the three responses in 550-700 msec. and 700-1100 msec., respectively. Our findings imply that insight is dominated by right hemisphere and can be represented by neural activity of abnegating the strongly salient options but accepting the weakly remote associative meaning.

Key words: insight, event related potential, three-character riddles, hemispheric effect, problem solving