Our third heuristic is the availability heuristic. We use this when we judge the likelihood of an event or the correctness of a hypothesis based on how easily that hypothesis or event comes to mind. So, what's the likelihood that I'm going to be attacked by a shark if I go swimming in the ocean? Well, what we see is that with publicity around pretty rare events, people tend to overestimate the likelihood that things will happen to them. Why? Because the availability of those things might be saturated in the media; and you could think back to a litany of public health scares everywhere from anthrax, West Nile, the H1N1 influenza, avian flu, SARS, shark attacks—the list kind of really goes on and on. But in these situations, when they happen, people will overestimate the likelihood that they might be a victim of one of those health scares, for instance. And we overestimate these things because they are pretty memorable (even though they may be rare events) often because they are sensationalized or that they are very extreme or that there are pretty strong consequences if you became a victim, say, of a shark attack. So again, this is really sort of the availability heuristic at play and how it operates.