Most previous research on facial signaling in cats has focused on interactions between cats and humans or assessing when a cat is in pain. The new study takes that a step further by analyzing how cats interact with one another.

And what better place to do that, than a cat café? After 150 hours at the CatCafe Lounge in Los Angeles, California, a nonprofit shelter where visitors can meet up to 30 cats for potential adoption. (What do cats think about us? You may be surprised.)

Their observations of 53 domestic shorthair cats revealed a wide variety of expressions—which combine various movements of the eyes, ears, and lips—and that most of these were friendly, not aggressive. Many cat people would instantly recognize some of these as friendly, such as ears and whiskers forward and eyes closed.

But some, like what the researchers call “play face,” with ears and whiskers forward and mouth pulled back at the corners, don’t have such obvious meanings.

What’s more, a lip lick might suggest a cat is anticipating a treat, but when combined with narrowed pupils and flattened ears, it’s an unfriendly cue.

Whiskers overall are surprisingly telling: Content or happy cats almost always point their whiskers forward.

Is that a fake smile?

After hours at the cat café, Scott recorded 194 minutes of cat interactions, excluding non-communicative behaviors such as yawning or chewing.

Back at the lab, the team used a coding system for facial expressions called Facial Action Coding System, or CatFACS. Trained users can identify “even the most subtle of muscle movements, and each of these movements, called an “action unit,” is noted and given a number using a video software, ELAN. This allows users to create and edit a video-footage timeline, which can read expressions at the millisecond level.

The analysis revealed 26 unique muscle movements that, in various combinations, created 276 facial expressions. The results categorized 46 percent of expressions as friendly, while 37 were unfriendly, and 17 fell into both categories.

Examining the facial expressions at such a granular level can catch nuances. A good example is the real vs. fake smile in humans: Though in both situations you’re smiling, there may be small differences, say in eye movements, that can indicate whether you’re actually happy. (Read surprising things you never knew about your cat.)

For some feline expressions, though, the meanings are still a mystery, and the team is planning follow-up studies to figure them out.

A tool for improving cat welfare

It will be really interesting to see what groupings are more common in different situations and contexts.

Cats don’t need eye contact to make their intentions known. Body posture and other behaviors, such as guarding a food bowl, sends a signal that “this is mine,” without needing to make any facial expressions.

Research could inspire scientists to observe facial expressions in wild cat species, which are more solitary. Knowing whether wild cats share specific meaningful expressions would discern whether domestication led to a greater variety of expressions in domestic cats. (Learn why cats domesticated themselves.)

The research also has a practical application, says Bennett, who consults with shelter organizations. For instance, the study could help develop a standardized tool of facial expressions, allowing animal shelter staff and volunteers to identify certain cues and act accordingly.

In one scenario, if two cats are brought into the shelter together, they may be considered to be bonded. But recognizing differences in their facial expressions could suggest otherwise, and point the staff toward finding a more suitable feline friend.

“I’m excited about this, They definitely think they’re on the right track.”