Burke Harris details the stress response by using two narratives, one about a drive-by shooting and another about scary bears. She opens with an anecdote about witnessing a drive-by shooting that severely injured a victim; Burke Harris had already completed medical school at the time, and under the influence of adrenaline and this training, she went into autopilot mode to help the victim (he died, unfortunately). This traumatic event initially left her sensitive to cars that looked like the shooter’s and to sounds like gunshots. Essentially, her body remembered what it felt like to be in danger in the presence of violence.

That stress response, Burke Harris notes, is an adaptation that allowed our ancestors to survive the many threats in their environment, so it’s a necessary part of human experience. Burke Harris explains that she was eventually able to move on from this response because she had almost no exposure to ACEs as a child and thus her mind and body were capable of not overreacting to these triggers as time went on.

By contrast, the bodies of children dealing with repeated and extreme threats after already having many ACEs at an early age can’t turn off their stress response.