The new report, published in the journal Frontiers in Psychology, analyzed the eating habits of more than 1,000 young adults ages 17 to 25. Researchers gave participants a test to measure for the “Big Five” personality traits: openness to experience, conscientiousness, extroversion, agreeableness, and neuroticism. Then they assigned some participants to keep a food diary for 21 days and others for 13 days, in hopes of encouraging more people to complete the task.