Fair warning: Reading this story might make you yawn.

But one of the biggest unsolved questions is why mammals yawn in response to one another.

In a new study, researchers examined contagious yawning in wild lions in South Africa. After being “infected” by others’ yawns, these lions tended to coordinate their movements.

“The data showed a clear picture: After yawning together, two lions would engage in highly synchronous behavior,” says study senior author Elisabetta Palagi, an ethologist at the University of Pisa in Pisa, Italy. (Here’s how we know animals can think and feel like us.)

This means contagious yawning could be especially important in social species such as lions, which must work together to hunt, rear cubs,