In a word, this book is about “thin-slicing:” the automatic act of perceiving minutia and forming snap judgements based on them. The author shows several impressive examples of how more information does not always lead to better results. In one particularly interesting example, it told of how an urban, over-capacity hospital learned to streamline the process of assessing chest pain risk by following a three-question algorithm. Diagnosing based on only these three questions lead to a drastic improvement in correct assessments, and reduction of time spent diagnosing, than assessments that took into account much more information, including family history, history of illness, recent stressors, etc.
The reason? These factors, while indeed influencing the overall risk, are insignificant contributors compared to the three algorithmic questions and inclusion of these factors lead to an exaggerated emphasis on these questions, mucking up the diagnosis.
There’s other examples of impressive near automatic analyses: one learned to predict—with 95% accuracy—whether a newly wed couple will divorce just by watching them discuss an issue of contention for 15 minutes. Another story: a tennis trainer could almost always tell if a player was going to fault before he/she hit the ball. Even more: art critics were able to instantly tell a highly valuable ancient statue was a fake, contradicting scientific and financial records. The kicker: none of them could explain why they knew, it was only a “gut feeling.”
There are experts who spend years observing and learning specialized traits and this training allows them to unconsciously judge specific details and arrive at amazingly accurate conclusions, yet they are unable to consciously explain the factors that influenced this decision.
He goes into further stories, telling of the ability to read facial expressions and interpret emotions, Pepsi vs. New Coke, autism, ergonomic chair design, and a fatal shooting of an innocent victim by cops who incorrectly assessed a situation. Overall, fascinating read that at first convinces you to pay more attention to your snap judgements, then shows the downside of snap judgements, and at the end, demonstrates that most people do an absolutely terrible job of explaining why they feel, want, or do certain things.