The tendency to overestimate the likelihood of events with greater “availability” in memory, which can be influenced by how recent the memories are or how unusual or emotionally charged they may be ,
One of the most useful findings of modern psychology is what Daniel Kahneman calls the Availability Bias or Heuristic: We tend to most easily recall what is salient, important, frequent, and recent. The brain has its own energy-saving and inertial tendencies that we have little control over – the availability heuristic is likely one of them. Having a truly comprehensive memory would be debilitating. Some sub-examples of the availability heuristic include the Anchoring and Sunk Cost Tendencies.
The availability bias is the human tendency to think that examples of things that come readily to mind are more representative than is actually the case. The psychological phenomenon is just one of a number of cognitive biases that hamper critical thinking and, as a result, the validity of our decisions.
The availability bias results from a cognitive shortcut known as the availability heuristic, defined as the reliance on those things that we immediately think of to enable quick decisions and judgments. That reliance helps us avoid laborious fact-checking and analysis but increases the likelihood that our decisions will be flawed.
Naturally, the things that are most memorable can be brought to mind most quickly. However, there are a number of factors that influence how well we remember things. For example, we tend to remember things that we observed ourselves more easily than things that we only heard about. So, for example, if we personally know of several startups and all of them are successful, we are likely to overestimate the percentage of startups that succeed, even if we have read statistics to the contrary.
Similarly, people remember vivid events like plane crashes and lottery wins, leading some of us to overestimate the likelihood that our plane will crash or, more optimistically — but equally erroneously — that we will win the lottery. In these cases, the availability bias leads some people to avoid flying at all costs and leads others to rely on a big lottery win as a retirement plan.