One of the biases that people rely on when they make decisions is loss aversion: like in the insurance example above, they tend to overweight small probabilities to guard against losses. Even though the likelihood of a costly event may be miniscule, we would rather agree to a smaller, sure loss — in the form of an insurance payment — than risk a large expense. The perceived likelihood of a major health problem is greater than the actual probability of such an event actually occurring.
We would all like to believe that we are logical decision makers. In the field of user experience, we often talk about how users weigh the expected utility of different alternatives to determine what action to take or where to go next. However, when it comes to making decisions such as whether to purchase something, make a donation, or pick a level of a service, people are highly susceptible to cognitive biases, and often don’t make the logical choice.
For example, what would you choose: to get $900 or take a 90% chance of winning $1000 (and a 10% chance of winning 0)? Most people avoid the risk and take the $900, although the expected outcome is the same in both cases. However, if I asked you to choose between losing $900 and take a 90% chance of losing $1000, most of you would probably prefer the second option (with the 90% chance of losing $1000) and thus engage in the risk-seeking behavior in the hope to avoid the loss.