关键词: 利他动机, 利己动机, 欺骗, 事件相关电位, N2, P3

Abstract: People tell lies not only for their own self-interests but sometimes also to help others. Little is known about the ways in which different types of goals modulate behaviors and neural responses in deception. The present study investigated the behavioral and neural processes associated with spontaneous deception triggered by different levels of altruistic motivation (the charity project rated high or low on the willingness of helping scale receive the money the participants won in the game) and self-serving motivation ( the participant self gets the money he/she won in the game). Twenty-four right-handed participants (12 males, age: 18.5±0.8 years (mean±s.e.)) participated in the present study, they were instructed to perform a coin-flip guessing task in which they could earn 5 RMB if they correctly predicted the outcome of a coin-flip and earn 0 RMB for an incorrect one. However, the distribution of the money they won was different in each block. In two of the three blocks, the money would be donated to a highest/lowest on the willingness of helping charity project chosen by the participant him/herself before the task; in the last block, the participants would gain all of the money they won. The order of the blocks was counterbalanced among participants. In each block, half of the trials, the participants recorded their prediction by a button-pressing before the coin-flip (they did not have the opportunity to lie without being caught; NoOp condition). In each NoOP trials, after a 1000ms fixation, the Chinese Words ‘Shuzi’ and ‘Hauwen’ would appear on each side of the screen for 3000ms and the participants were instructed to record their prediction by pressing the button ‘F’ if they predicted ‘head’(“数字”) and the button ‘J’ if they predicted ‘tail’ (“花纹”) for that particular trial. After pressing, the outcome of the coin flip would appear for 2000ms. Then, the question ‘Correct?’ appeared on the screen next, the participants were instructed to indicate whether their prediction was correct by pressing the Y key for ‘Yes’ or the N key for ‘No’. After the response, a screen would show how much money the participant earned in this trial for 1000ms. The other half of the trials was opportunity-to-deceive-without-being-caught trials (Op). While in the other half of the trials; they only needed to make a mental prediction. The structure of the Op trials was the same as the NoOp trials. The only difference was instead of the head and tail in the NoOP trials, the word ‘Random’ would appear on both side of the screen for 3000 ms. When the word ‘Random’ appeared, the participants would make a prediction mentally and press the ‘R’ key to indicate they finished their prediction. The Op condition allowed the participants to freely engage in voluntary deception by over-reporting the accuracy of their prediction without being detected. EEG during the task were recorded and the ERPs when they observing the outcome of the coin-flip were analyzed. Results showed that the patterns on behavioral response and ERP data in high level of altruistic motivation and low level of altruistic motivation are high correlated. Behaviorally, the participant who lied more under high level of altruistic motivation also lied more in the low level of altruistic motivation, and both of the degree of lying negatively correlated with the participants’ PD score. Neurally, the difference of N2 and P3 between Op and NoOp conditions were only significant in the self-serving condition, but not in the altruistic condition. Combined with behavioral and ERP findings, it can be concluded that deceptive behavior under altruistic motives is fundamentally different from deceptive behavior under self-serving motives, and that there is only a qualitative difference between deceptive motives based on different levels of altruism, with no qualitative differences. We also find PD empathy traits play an important regulatory role in altruistic motivated deception, the individual with higher PD scores, and the less deceptive to achieve altruistic goals. These findings shed light on the neural basis of “white lies”.

Key words: altruistic motivation, egoistic motivation, deception, event-related potentials, N2, P3