2013年10月29日火曜日

Neural Underpinnings of the Identifiable Victim Effect: Affect Shifts Preferences for Giving

Alexander Genevsky, Daniel Vastfjall, Paul Slovic, and Brian Knutson
J. Neurosci. 2013;33 17188-17196 Open Access

ヒトfMRI。
「匿名の他人」よりも「顔/名前などが分かっている他人」を助けたくなるという「identifiable victim effect」の神経基盤を研究。
「他人の顔写真を見ることができるケース」と「影絵のみのケース」を比較。
行動データ:顔写真が見られるケースの方が、他者に対する寄付額が大きくなる。
fMRIデータ:顔写真が見られるケースでは情動関連や顔認知関連の様々な脳部位が活動するが、その中で「腹側線条体の側坐核(nucleus accumbens)」だけが寄付額を予測出来る。

The “identifiable victim effect” refers to peoples' tendency to preferentially give to identified versus anonymous victims of misfortune, and has been proposed to partly depend on affect. By soliciting charitable donations from human subjects during behavioral and neural (i.e., functional magnetic resonance imaging) experiments, we sought to determine whether and how affect might promote the identifiable victim effect. Behaviorally, subjects gave more to orphans depicted by photographs versus silhouettes, and their shift in preferences was mediated by photograph-induced feelings of positive arousal, but not negative arousal. Neurally, while photographs versus silhouettes elicited activity in widespread circuits associated with facial and affective processing, only nucleus accumbens activity predicted and could statistically account for increased donations. Together, these findings suggest that presenting evaluable identifiable information can recruit positive arousal, which then promotes giving. We propose that affect elicited by identifiable stimuli can compel people to give more to strangers, even despite costs to the self.

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