Caste: The Origins of Our Discontents

by Isabel Wilkerson

The threat they perceived as a result of their prejudice set off their body’s alarm system. Their panic produced automatic physiological responses as would occur if they were in combat or confronting an oncoming car—restricted blood flow to the heart, the flooding of the muscles with glucose as the body releases cortisol, the hormone useful in the rare moment when one might need to escape danger, but damaging to the body on a regular basis. The combination of reduced blood flow, constrictions to the circulatory and digestive systems, and the breakdown of muscle by cortisol can lead to life-threatening damage to the heart and the immune system and to death before one’s time. Even the briefest exposure is all it takes to activate the body’s response. Among whites, the sight of a black person, even in faded yearbook photographs, can trigger the amygdala of the brain to perceive threat and arm itself for vigilance within 30 milliseconds of exposure, the blink of an eye, researchers have found. When whites have a bit more time for the conscious mind to override the automatic feeling of threat, the amygdala activity switches to inhibition mode. When whites are prompted to think of the black person as an individual, imagine their personal characteristics, the threat level falls.