2013年10月3日木曜日

The Neural Basis of Following Advice

Biele G, Rieskamp J, Krugel LK, Heekeren HR
PLoS Biol 2011 9(6): e1001089. doi:10.1371/journal.pbio.1001089

報酬予測/強化学習(道具的条件づけ)に「他者からのアドバイス(学習を行う前に、一度だけ与えられる)」はどのように影響するか?
(1)被験者は「他者のアドバイス」に従う傾向がある。つまり、他者が奨めた選択肢を選びやすい。
(2)「価値(報酬予測)の初期値」に影響を与えるだけでなく、学習の過程全般にわたって影響を与える。
(3)具体的には、「強化子=実際の報酬+アドバイス・ボーナス」という形で学習に効いてくる。
(4)アドバイス・ボーナスは、報酬を処理する脳部位「尾状核(Caudate)」でコードされている。

Learning by following explicit advice is fundamental for human cultural evolution, yet the neurobiology of adaptive social learning is largely unknown. Here, we used simulations to analyze the adaptive value of social learning mechanisms, computational modeling of behavioral data to describe cognitive mechanisms involved in social learning, and model-based functional magnetic resonance imaging (fMRI) to identify the neurobiological basis of following advice. One-time advice received before learning had a sustained influence on people’s learning processes. This was best explained by social learning mechanisms implementing a more positive evaluation of the outcomes from recommended options. Computer simulations showed that this ‘‘outcome-bonus’’ accumulates more rewards than an alternative mechanism implementing higher initial reward expectation for recommended options. fMRI results revealed a neural outcome-bonus signal in the septal area and the left caudate. This neural signal coded rewards in the absence of advice, and crucially, it signaled greater positive rewards for positive and negative feedback after recommended rather than after non-recommended choices. Hence, our results indicate that following advice is intrinsically rewarding. A positive correlation between the model’s outcome-bonus parameter and amygdala activity after positive feedback directly relates the computational model to brain activity. These results advance the understanding of social learning by providing a neurobiological account for adaptive learning from advice.

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