Individuals are the fundamental units of society, yet when people aggregate into crowds, new patterns of behavior and insight emerge that cannot be predicted by examining individuals alone.

First impressions feel decisive. Within seconds of meeting someone, evaluating a product, or scanning a résumé, we experience a strong sense of clarity: competent or incompetent, trustworthy or suspicious, impressive or mediocre.

We’ve all heard it: “Follow your passion, and everything will fall into place.” It’s stitched into graduation speeches, echoed in self-help books, and plastered across motivational posters.

We all like to think of ourselves as rational beings. We make choices, form opinions, and draw conclusions based on logic—or so we tell ourselves.