There are only 4 personality types, study says: Which one are you?

02:25

A new study on human behavior puts 90 percent of the population into just four personality categories: envious, optimistic, pessimistic and trusting. Al Roker thinks he’s an optimist, as do Hoda Kotb, Savannah Guthrie and Matt Lauer, but Carson Daly says he’s trusting. We trust Carson!