The availability heuristic is a rule of thumb, where people base their prediction of the frequency of an event or the proportion within a population based on how easily an example can be brought to mind.  One can think of many examples of the “availability heuristic” in everyday life.  For instance, you may be an experienced driver. Over time you have learned that when you come to a stop sign, you need to come to a complete stop or you will get a ticket. Now, whenever you come to a stop sign, you have to give very little thought at all to what behaviour is required; you see the stop sign, you stop. You have a heuristic for stop signs.