You go to take a step up onto your porch when you realize it’s covered in shimmering, slippery ice. Your mind wants to stop so you don’t hurt yourself, but your body isn’t going to get the message in time. Here’s what’s going on in that brain of yours.
According to a recent study conducted by Johns Hopkins University neuroscientists, and published in the journal Neuron, we only have a few milliseconds to change our minds and stop our actions after the initial go-ahead signal sent by our brains. That’s why we often know we’re making a mistake while it happens. Previously, scientists thought that only one region of the brain was active when people attempted to alter course, but they’ve now realized that halting yourself in such a way requires speedy choreography between several different areas of your brain, and as we age that becomes more difficult. As senior author Susan Courtney points out, three areas of the brain have to communicate successfully in order for us to stop—including the “oops” area of the brain where Courtney says we continue to conclude what we should have done—and the whole process has to happen very quickly.
Kitty Z. Xu, the first author of the study, explains the process with an example of driving and approaching an intersection when the light has just turned yellow. Your brain decides to accelerate and speed through, and as soon as you do you notice a police car watching and change your mind. You want to hit the brakes instead, but it’s too late:
“Which plan is going to win? The sooner you see the police car after deciding to go through the light, the better your chance of being able to move your foot to the brake instead... If you’re already executing the plan when you see the police car, you’re going to go through the light.”
According to Xu, you have milliseconds to notice the police car and change your course of action (less than 200 milliseconds, or less than a quarter of a second, to be exact). Take any longer and you’ll speed on through, and curse up and down while you wonder “Why am I doing this?!” The answer: the original signal was already on its way to your muscles and past the point of no return. Basically, our brains think faster than our muscles can respond, and altering our actions is more difficult than we once thought.