Do your true friends also consider you to be a close companion? Most people expect their feelings of friendship are shared, perhaps with the odd exception of a glamorous acquaintance they’re hoping to befriend, but newly published research suggests we’re actually quite poor at judging whether friendship is reciprocated.

Researchers from Tel Aviv University and MIT surveyed 84 students in an undergraduate course, asking them to rate their relationship with others on a scale from 0 (don’t know them) to 5 (they’re one of my best friends). In 94% of cases, a subject who said another person was a friend expected to be viewed as a friend in return. But in fact, the researchers found, only half the friendships were reciprocal.

Similar results were found when the researchers analyzed data from five previous friendship surveys of 600 students from universities in Europe, the US, and the Middle East. The researchers also reviewed a previous study of adolescents, which found that just 64% of the reported friendships were reciprocal.

The authors reason that unreciprocated friendships are likely connected to social status and power hierarchy. They write:

“This suggests that many of the non-reciprocal friendships are aspirational: people want to be friends with higher-status individuals and behave in ways that indicate friendship (e.g., naming them as friends), but higher-status individuals have greater choice in which friendships to reciprocate and choose to only behave as a friend to a subset of the friendships offered to them.”

The authors then developed an algorithm to predict the reciprocity of friendship, and found that “social embeddedness,” namely the extent to which two subjects’ friendship circles overlap, and “social centrality,” or the difference in each person’s social hierarchical status, were strong indicators of whether a friendship would be two-way.

It’s disquieting to think that we could be so poor at judging who our friends are. But it’s important to note that the researchers didn’t distinguish between people who are “friends” because they’ve taken a course together, and close friends who have known each other for years. There are a few key signs of friendship that don’t need to be validated by a survey. Chances are if you’ve seen someone cry, helped them through a difficult period, or simply drunk enough glasses of wine with them, then you can consider them a true friend. But that beautifully-dressed comedian you met at a party? Maybe she’s not your best pal just yet.