The clustering illusion is the illusion that random events which occur in clusters are not really random events. The illusion is due to a counter-intuitive assumption about statistical odds. For example, it strikes most people as unexpected if heads comes up four times in a row during a series of coin flips. Now if you have got 3 consecutive heads, you’d think next flip can’t be heads, though there is still a 50% probability. Thinking that the probabilities have changed is a common bias. This has caused gamers to lose thinking the probability has changed.