Research highlight

Human behaviour: Racial biases change in a heartbeat

Nature Communications

January 18, 2017

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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