Heart beat affects danger perception.

In Brain General Structure and Function, Brain Science, Senses and Perception by Brainy Days Ahead

New research concludes that our heartbeat can increase pre-existing racial biases when we face a potential threat. Researchers at Royal Holloway, University of London, working with Brighton and Sussex Medical School found that study participants were likely to misperceive a situation involving a black person as life-threatening, when experienced during a heartbeat rather than between heartbeats. The research could lead to the development of new approaches to responding to threatening situations.