Here’s the question: someone approaches you, but are they flirting or just being polite? Nonverbal communication—especially facial expressions—plays a crucial role in how we interpret someone’s romantic intentions.

A study by Emily S. Bibby, Allison M. McKinnon, Michael Shaw, and Richard E. Mattson, titled “Accurately Detecting Happy Facial Expressions Associates with Perceptions of Flirtatiousness,” found that our ability to correctly read happy expressions directly affects whether we perceive someone as flirting. The findings are clear:

Some people misread neutral, angry, or surprised expressions as a smile, interpreting them as positive—and possibly romantic. These individuals tend to overestimate others’ flirtatious intentions, thinking someone is flirting when they’re not. This doesn’t mean they’re naive or overly imaginative; rather, their perception reflects a desire for social acceptance. They see flirtation because they subconsciously hope it’s there, interpreting social cues through an “optimistic lens,” even at the risk of misreading the situation.