We tend to adopt the actions of people surrounding us. In a study from Leeds University, researchers asked volunteers to walk around a venue without talking to each other, and provided a select few with instructions on where to walk. They found that it took only 5 percent of people in the crowd to influence the rest—the other 95 percent of participants followed without even realizing it. On the one hand, herd mentality creates functioning communities and societies, on the other hand, it can lead us to subconsciously follow the crowd when it’s not in our best interest.
We tend to search for and interpret evidence as confirmation of our existing beliefs or theories. A study out of Stanford provided people on both sides of the capital punishment debate with two studies: one supporting and one disconfirming their beliefs—both groups rated the study that confirmed their beliefs as more convincing. While this bias helps us make small decisions more efficiently based on what we already know, it can lead to poor choices in complex decisions because we don’t consider all of the facts uniformly.
We believe our personal futures will be better than our past or present, which leads us to overestimate the positive outcomes of our efforts or experiences. Research from Rutgers University found that smokers underestimate their relative risk of lung cancer compared to non-smokers, and believe they have a lower risk of developing lung cancer than the average smoker. Optimism bias inspires us to strive for a better future, but it can also lead to poor decisions due to our miscalculated outcomes.