2013年10月13日日曜日

Imaging Social Motivation: Distinct Brain Mechanisms Drive Effort Production during Collaboration versus Competition

Raphael Le Bouc and Mathias Pessiglione
J. Neurosci. 2013;33 15894-15902

ヒトfMRI。
【実験課題】
基本的には、「ハンドグリップを握る強さに応じて報酬が得られる」という課題。
三条件あり、それぞれ「自分の握りの強さ(個人条件)」、「自分と他者の握りの強さの平均(恊働条件)」、「自分と他者の握りの強さの差(競争条件)」に応じて報酬が貰える。
【結果】
行動:被験者は恊働条件で、個人条件に比べて、強い力でグリップを握った。一方、競争条件では個人条件との差は見られなかった。
fMRI:「恊働条件で(個人条件に比べて)より強い力を出した被験者」は「TPJ(側頭頭頂接合部)が恊働条件で強く賦活して」おり、さらに「TPJの灰白質の体積が大きい」ことが分かった。
【結論】
「自分の報酬/コストの最大化を目指すなら、恊働条件では力を緩めるべきである」にも関わらず、ヒトは他者と恊働するときに、単独での場合と比べて、大きな力を出す。
そして、その傾向はTPJの活動によってもたらされる。

Collaborative and competitive interactions have been investigated extensively so as to understand how the brain makes choices in the context of strategic games, yet such interactions are known to influence a more basic dimension of behavior: the energy invested in the task. The cognitive mechanisms that motivate effort production in social situations remain poorly understood, and their neural counterparts have not been explored so far. A dominant idea is that the motivation provided by the social context is reducible to the personal utility of effort production, which decreases in collaboration and increases in competition. Using functional magnetic resonance imaging, we scanned human participants while they produced a physical effort in a collaborative or competitive context. We found that motivation was indeed primarily driven by personal utility, which was reflected in brain regions devoted to reward processing (the ventral basal ganglia). However, subjects who departed from utility maximization, working more in collaborative situations, showed greater functional activation and anatomical volume in a brain region implicated previously in social cognition (the temporoparietal junction). Therefore, this region might mediate a purely pro-social motivation to produce greater effort in the context of collaboration. More generally, our findings suggest that the individual propensity to invest energy in collaborative work might have an identifiable counterpart in the brain functional architecture.

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