“Such “trained intuition” is a large part of what distinguishes experts from amateurs in most fields. We don’t always consciously know what it is that doesn’t fit, but somewhere our brain recognizes that part of the puzzle is missing, and it sends up a signal that something’s askew. (This “gut feeling” is actually a low-level activation of the stress response system, which is acutely attuned to combinations of incoming signals that are out of context or novel.)”