The availability heuristic is a rule that we tend to apply when we make judgements. This mental shortcut suggests that we give importance to things that are easier to recall to mind and we give less importance to things that are harder to recall.
Although the availability heuristic can be very effective when we make judgements, it can also produce several errors. A classic example of this concerns airplane accidents. Because airplane accidents usually receive more publicity in the media than car crashes, the availability heuristic leads people to erroneously believe that airplanes are more dangerous than cars. However, when you look at the statistics, you are much more likely to die in an auto accident than a airplane accident.
The availability heuristic, like many other heuristics, shows us that although our gut instinct is often right, there are some instances where our subjective feelings are incorrect and we should instead rely on something more objective.