Olympic skiers, bobsledders and speed skaters all have to master one critical moment: when to start. As athletes prepare for the upcoming Winter Olympics, that split second is in the spotlight because when everyone is fast, strong and skilled, a moment of hesitation can separate gold from silver. Research from Carnegie Mellon University helps explain why that split-second pause happens and how the brain controls it, offering insight not only into elite athletic performance, but also how people make everyday decisions when the outcome isn’t clear.

Eric Yttri, associate professor of biological sciences, wanted to study how the brain decides when to act and when to wait, especially when the outcome is uncertain. He said to think about the moment the puck drops at a heated rivalry hockey game.

“Move too early, you get ejected from the faceoff. Move too late, and the puck is already gone. Having that sort of fine control on your ability to delay your action is really key,” Yttri said. “It’s a sword that cuts both ways.”