In chapter 4, Gladwell continues his purpose to extol the value of "thin-slicing," or those insightful first impressions, and begins discussing how we can control those impressions to our benefit. Here he begins with the story of the Millennium Challenge, a war game conducted in 2000 by the U.S. Joint Forces Command. His point in this story is that Paul van Riper, a retired Marine Corps general who acted as the rogue commander, used the power of first impressions within a set of guidelines to win the challenge against his data-driven opponent. He won by allowing his field personnel the freedom to act on gut instincts during the heat of "battle."
Gladwell takes this concept into the civilian world when he examines the improvisational acting group Mother. Spontaneity is the key to good improv. Only when acting on their split-second instincts can actors create side-splitting comedy. Yet the acting troupe provided a general rule for their thin-slicing: Say yes to everything. This shows how we can control and use our thin-slicing ability to our benefit.
Gladwell then goes on to discuss the "perils of introspection" and warn against overthinking problems and relying too heavily on too much data. The example of doctors in the emergency room trying to diagnose heart attacks shows that by developing an algorithm that uses only the most applicable data, doctors can then use their instincts to give patients better care.
Chapter 4 is key to Gladwell's premise in the Introduction that "we can . . . teach ourselves to make better snap judgments." Here he introduces the reader to "doctors and generals . . . [who] owe their success, at least in part, to the steps they have taken to shape and manage and educate their unconscious reactions."