Do birds of a feather really flock together? The science says yes. People do tend to choose friends who are similar to them. You also become more like your friends over time. And that can influence your health. Many behaviors spread socially. Examples include how much you exercise, how much alcohol you drink, whether you smoke, and what foods you eat. Scientists are still trying to untangle why that is. Studies have found that activity in certain brain areas changes when other people are around. That can affect what you choose to do. But this work also suggests that you can harness the power of social relationships to gain healthier habits—and motivate others to do the same. Social Influence “People care about what others think across all different age groups—and that influences how much they value different ideas and behaviors,” says Dr. Emily Falk at the University of Pennsylvania. She …