为什么一个人在大庭广众之下会感到压力，甚至犯一些低级错误？据美国媒体9月6日报道，美国南加利福尼亚大学的最新研究从大脑生理基础方面解释了为什么一个人被亲朋好友或观众盯着看时，往往会犯一些他在独处时绝不会犯的错误。研究论文发表在本月出版的《美国国家科学院院刊》上。
新研究发现，人在社会环境中，其大脑会比在独处时更加重视胜利。南加利福尼亚大学多恩斯夫文学艺术与科学学院乔治奥·科瑞塞利领导的一个跨国研究小组，对参加有奖游戏的人进行了脑部检测，检查他们在参与游戏时，与报偿机制和社会理性相关的脑区活动情况。结果发现，当参与者在有奖游戏中击败了实力相当的对手时，他们大脑中与报偿机制相关的区域——纹状体显出了更高的活跃性，这和他一个人玩而获胜时表现出的情况截然不同；而和社会理性相关的脑区——内侧额叶前皮质也表现得更加活跃。
“这表明大脑具有察觉社会信号的能力，并能对这种信号给予编码，让其更加突出，然后使用这些信号指导下一步的行为，以达到未来行为最优化。”科瑞塞利解释说，一方面参与者在社会环境中获胜，可能伴随着更多风险，使他们在随后的游戏中遭遇更多竞争；另一方面，群体环境中的报偿机制倾向于让“赢家获得一切”，这在关乎繁衍后代的配偶竞争中尤其明显，正如传奇赛车手戴尔·恩哈特的名言：第二名只是第一个失败者。
“在动物界同样存在强烈的刺激机制，驱动个体攀登其社会阶级的顶层。处于统治地位的动物，会用它们的地位来保卫自己获得资源的特权，如食物和配偶。”科瑞塞利说，但无论怎样，当一个人处在群体中时，他所获得的回报总是大于风险。而在私人环境中，尤其在没有社会网络支持的地方，失误更可能带来生命威胁，一次失败的赌博可能导致灾难。(生物谷 Bioon.com)
doi:10.1073/pnas.1100892108
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Medial prefrontal cortex and striatum mediate the influence of social comparison on the decision process
Nadège Bault, Mateus Joffily, Aldo Rustichini, and Giorgio Coricelli
We compared private and social decision making to investigate the neural underpinnings of the effect of social comparison on risky choices. We measured brain activity using functional MRI while participants chose between two lotteries: in the private condition, they observed the outcome of the unchosen lottery, and in the social condition, the outcome of the lottery chosen by another person. The striatum, a reward-related brain structure, showed higher activity when participants won more than their counterpart (social gains) compared with winning in isolation and lower activity when they won less than their counterpart (social loss) compared with private loss. The medial prefrontal cortex, implicated in social reasoning, was more activated by social gains than all other events. Sensitivity to social gains influenced both brain activity and behavior during subsequent choices. Specifically, striatal activity associated with social gains predicted medial prefrontal cortex activity during social choices, and experienced social gains induced more risky and competitive behavior in later trials. These results show that interplay between reward and social reasoning networks mediates the influence of social comparison on the decision process.
