Research press release


Nature Communications

Human behaviour: Racial biases change in a heartbeat



今回、Manos Tsakiris、Ruben Azevedoたちの研究チームは、心臓から脳に送られる信号が人種的偏見の表現に及ぼす影響を調べるために、人種的偏見を測定するために一般的に使用される試験(weapons identification taskとfirst person shooter task)に参加した32人の被験者の心拍を監視した。それぞれの検査では、あらかじめ白人の顔を見せられた被験者と黒人の顔を見せられた被験者に刺激(拳銃(標的)または携帯電話、手工具などの害を及ぼさない物体)を実際に与えて、この刺激を武器と誤認した者が占める割合を比較した。その結果、黒人の顔によるプライミング刺激を与えられた被験者の方が武器と誤認することが多いことが判明した。今回の研究では、このプライミング刺激を与える時期が被験者の心拍との関係で注意深く制御された。そして、Tsakirisたちは、黒人が害を及ぼさない物体を所持している場合にその物体を武器と誤認する確率が高くなるという人種的偏見の表現が主に観察されるのは、心臓の拡張期ではなく収縮期に顔の刺激が提示された場合であることを明らかにした。


Expression of some racial biases may be modulated by the signals that our heart sends to the brain on every beat, reports a study published in Nature Communications. The research shows that perception of threat based on pre-existing racial biases differs depending on whether the information is processed during or between heartbeats.

Previous research has demonstrated that harmless objects are misidentified as weapons more often when held by black individuals than by white individuals. Studies have also suggested that in some people, faces of black individuals activate threat signalling in the brain and this bias is exaggerated in states of anxiety and stress. In addition, emotional stimuli have been shown to be perceived more intensely based on the level of cardiovascular arousal, which influences brain activity.

To investigate the influence of the signals from the heart to the brain on the expression of racial bias, Manos Tsakiris, Ruben Azevedo and colleagues monitored the heart rhythm in 32 people participating in tests that are routinely used to measure racial bias: the weapons identification task and the first person shooter task. In both tasks a face of either a white or a black man is shown before the actual test stimulus, which could be either a gun (target) or harmless objects such as a phone or hand tool, and the proportion of weapon misidentification is compared. Subjects misidentify objects as weapons more often when ‘primed’ with a black face. Here the researchers carefully controlled the timing of this priming stimulus in relation to the participants’ heartbeats. They found that racial bias, expressed as a greater likelihood to perceive harmless object as a gun when held by a black individual, was mainly observed when the face stimuli were presented during the heartbeat, rather than between heartbeats.

doi: 10.1038/ncomms13854

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