Over confidence in our ability to assess risks has led to more mistakes than we care to admit. WYSIATI - "What You See Is All There Is" describes a set of biases that prevents us from becoming better risk managers. Why is this the case? Because we jump to conclusions based on weak evidence and confuse correlation with causation.
Our brains are hard wired to jump to conclusions and serves us well in most cases but unfortunately leaves us vulnerable when novel risks present themselves or are hidden because of the blinders we put on when the evidence doesn't appear to be conclusive. My personal experience comes from not one but two separate incidences of life threatening bilateral pulmonary embolisms. I have always been an athlete and long after my career in sports ended I stayed active by running or exercising vigorously 4-5 days per week. Three years ago in felt a little run down and could not complete my normal 7 mile run as usual. That night I woke up in a sweat saturated bed, dizzy and could not breathe. I had little to no pulse but the incident passed quickly and I assumed it was the flu. The next day I could not climb the stairs and checked myself into the emergency room.
When the attending hospitalist came in to see me after checking my chest MRI and the sonogram of my legs asked me how I felt. I said I felt great and couldn't wait to get out to go on a trip I had planned. Needless to say the trip got cancelled. You see I had a full leg Deep Vein Thrombosis which eventually led to a massive bilateral pulmonary embolism. WYSIATI - prevented me from detecting anything wrong because I was not looking for blood clots as the cause of my undersperformance on the track. Three years hence I had a second attacck but this time I caught on to the symptoms early and got to the hospital early preventing the surgery that I needed to remove the clot in my legs in the previous incident.
Because of my conditioning my heart rate, blood pressure and other vital signs were not out of the normal range indicating problems even though both my lungs were filled with massive blod clots. We make these same mistakes every day with patient care, operational risks, and judgments about people who we know very little about.
Make sure that you don't accept WYSIATI as standard operating procedure. Be somewhat skeptical about the statisitics that you read. Much of research is subject to the same flaws because of the limited data that is used to draw broad conclusions about successful outcomes. Rule out overconfidence when you sense that there is something "off" but you can't put your finger on it.