Heuristics are the rules of thumb that guide most of our decisions in everyday life. Such heuristics work well for dealing with routine risks such as driving, using crosswalks, or avoiding social embarrassment. But outdoor adventures present unique hazards that render some of our heuristics irrelevant, and in some cases dangerously misleading. When a rule of thumb gives us a grossly inaccurate perception of a hazard, we fall into what is known as a heuristic trap.
Check out this great article on the topic by Ian McCammon: