I've been doing studies on trading gaps in stocks and YM and I was just wondering about the psychological aspect of it. It's statistically proven that the majority of normal gaps do get filled on the same day, but I was just wondering why this is exactly. Why does the price gravitate towards filling the gap? It's also a valid method to fade stocks that have just filled their gap and playing for a reversal. What is the logical reasoning behind all this, can anyone shed some light? I would imagine that if a stock gaps down overnight, a lot of people are going to want to sell if they can get the same price as yesterday's close, so that could be a valid explanation for why prices often reverse after the gap fills. Other than that, I'm looking for answers here.