• We know about Bill Gates or Mark Zuckerberg dropping out of college to start a billion-dollar business and we over-value that story in our heads. Meanwhile, we never really hear about all of the college dropouts that fail to start a successful company.
• We hear about a person from a particular ethnic or racial background getting arrested and we assume all people with that background are more likely to be involved in crime. We don't take into consideration the 99 percent of people who don't get arrested because it is a non-event.

We tend to overestimate the importance of events we can easily recall and underestimate the importance of events we have trouble recalling. 

The easier it is to remember, the more likely we are to create a strong relationship between two things that are weakly related or not related ...