January 14, 2016

Despite the peaceful lives we live most of the time, the human brain is hardwired for explosive violence. The neural circuits of rage react faster than the speed of thought. They have to. A mother, for example, will explode in violence to protect her child when the “hypothalamic attack region” deep in her brain senses a threat. We evolved these neural circuits for survival in the wild. We still need them.

But the modern world–with its wealth of stimuli–is utterly transformed from the environment in which our brain was designed to operate. This mismatch can lead to misfires. This month Shakira Green, 30, was arrested and charged with suddenly attacking her child’s second-grade teacher, Rosalind Simmons, in a classroom in Palm Beach, Fla. And years ago, Donald Bell made headlines for shooting and killing another motorist, Timothy Mann, in a Sacramento road-rage incident. (Two weeks later, he committed suicide.) This “snapping” is especially disturbing, because it can be triggered by seemingly benign acts, such as an offhand comment or gesture.

There is an upside, though. When it works as intended, the same neural circuitry that sparks rage can also spark stunning performances in fast-paced sports and selfless acts of heroism. “I didn’t think,” passenger Jasper Schuringa said in 2009, after he dived over rows of seats to subdue a terrorist attempting to set off a bomb on Northwest Flight 253. But he still acted smartly–and the rest of us can too. Understanding the brain’s threat-detection system is the first step to exploiting and controlling it.

Fields is the author of Why We Snap: Understanding the Rage Circuit in Your Brain

Contact us at editors@time.com.

This appears in the January 25, 2016 issue of TIME.

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