The Availability Bias, also known as the availability heuristic, is a state recognised in 1973 by psychologists Amos Tversky and Daniel Kahneman (if you’ve not read his book Thinking Fast and Slow, you really should!).
The basic principle is that it’s a mental trick whereby a person assigns a level of importance or likelihood to something based on how easily it comes to mind.
As an example, if your house has been recently burgled - you’re likely to put a much higher probability of burglaries in your neighbourhood, than a neighbour whose house hasn’t been burgled.
It’s a psychological trait that affects almost everyone and it’s very hard to avoid because it’s hardwired into the way our brain works.
The availability bias will have an impact in many areas of our life, including decisions at work. I’ve come to believe the greatest problems it can cause in web design is when taking feedback from clients.
For people who have been working on the project over an extended period, it typically becomes easier to take a properly objective view of decisions being made. For directors and stakeholders who have not been so involved, and are being asked for opinions only intermittently - it’s much more likely the feedback will have a strong availability bias.
Site navigation is a good example of this. As responsible UX designers, we will work hard to understand the audience and make it easy for them to find the most important and popular content. Part of this will usually mean moving navigation for less popular pages to a secondary position. Easily findable, but not intrusive.
All too often though, demands are made to put more links into the main navigation, because of an availability bias on the part of a department head or director who instantly looks for a particular section because it’s relevant to them - irrespective of the actual empirical evidence of how important that section might be.
I don’t have any magic solutions to this issue - but it does help to understand what’s potentially driving irrational feedback.