In the introduction to Outliers: The Story of Success, Malcolm Gladwell begins by giving the definition of the word outlier: a person, situation, or thing that is different from others. This definition of something that is markedly different from the normal or the average is the foundational principle of his book. Gladwell studies people and situations that are above average or that stand out from the norm, and he looks into all of the different factors that play a role in creating their success.

To explain the concept of an outlier in more depth, Gladwell describes the people of an Italian village named Roseto Valfortore. Many of these Italians emigrated and ended up all living in the same small town in Pennsylvania, which they named Roseto. Over time, they remained a close-knit community, closed off from the rest of the world for the most part.

What is interesting about their community in Pennsylvania is that hardly any of the men in the city suffer from heart disease. This was discovered in the 1950s when a doctor, Stewart Wolf, was traveling in the area. One of the local physicians told him that he rarely saw anyone from the small town of Roseto for heart disease. This intrigued Wolf, who then did extensive studies on the people of the town, including their physical makeup, culture, lifestyle, and all other possible factors that could play a role in heart disease.

What the physician discovered was quite interesting: people in the town right next to Roseto suffered from normal levels of heart disease, as did people who moved away from Roseto. Also, the Rosetans did not eat healthily, exercise much, or have very active lifestyles. Despite all of these factors, the Rosetan community still had hardly any heart disease. Wolf concluded that their lack of heart disease was caused by their attitude and lifestyle. The people in the community were close; they knew each other well, supported each other, said hello to each other, and lived with multiple generations in their homes. This close-knit support group was the only explanation for the lack of heart disease. It was concluded that Roseto, an outlier for being different from the norm when it came to heart disease, was healthy not because of individual efforts to stay healthy but because the people lived in a supportive environment surrounded by their close friends and family members.

Gladwell uses the example of Roseto to set up the premise of his book: successes and failures can be explained in unexpected ways; too often, we do not take those factors into consideration as much as we should.