His thesis in this book is that frequently instantaneous reaction yields much better decisions than the thoughtful gathering information and weighing it all. He has many case studies and interviews to support this thought.
One example is what happens in a hospital ER when doctors are trying to determine if a patient is having a heart attack. A quick decision is very important and the wrong decision leads to deaths or wastage of scarce resources that can also impact other patients. They found that just collecting a few basic pieces of info (BP, EKG, and pain evidence) was much more accurate than adding in many other factors (diet, parentage, certain blood tests which take time to get, etc.) One thought is that as you collect more information you begin to doubt what you've already learned.
He has an example of an expensive statue which careful studies by various experts convinced the museum that it was real. Yet several experts on first look within 2 seconds decided it was a fake. And careful studies showed it was a fake - $10mill down the drain.
Another issue is that preconceived notions have a very important impact. An example is with auditioning of musicians for classical orchestra positions. For many years there was a ingrained thought that women musicians weren't as good as men. This seemed to cause few women to be selected. Then many orchestras started doing auditions where the candidates were behind a curtain. In most cases the director can evaluate a musician after hearing a minute of less of playing. The sex, demeanor, nationality, sex, size, and other traits can cause the decision to not be based upon the musical talent but other factors. SInce auditions have now become standard behind the curtain there are many more women being chosen.
"Packaging" of products as well as musicians seems to have a big effect on what people like. As part of an example of people deciding which of two liquors they liked. The majority chose the one in the fancy bottle; a later experiment where the contents were reversed the majority again chose the liquor in the fancy bottle.