Extroversion
Research has repeatedly shown that introverts aren’t as happy as extroverts.
William Fleeson, Ph.D., asked 50 undergraduates in group discussions to act assertive and energetic. They later rated their emotions. He then repeated the experiment, but asked the same students to act shy and passive.
Without exception, when students acted extroverted, they indicated high levels of happiness and fun. When the same individuals acted introverted, they consistently rated themselves as unhappy. Extroversion, and by extension happiness, may be within our reach.