"If you're a pilot, you need to be able to monitor multiple instruments at the same time. If you're a cab driver, you need to pay attention to multiple events at the same time. If you're in the military, you need to multi-task too," she said. "On the other hand, if you're trying to solve a complex problem, you need sustained concentration. If you are doing a task that requires deep and sustained thought, multi-tasking is detrimental."