23 adult chimpanzees (Pan troglodytes) were separated into two groups, and were shown videos of familiar chimpanzees both yawning, and just going about their usual business, as well as videos of unfamiliar chimpanzees.
The video of the familiar chimapanzee yawning resulted in the subjects yawning - while the video of the familiar chimpanzee just being a chimpanzee showed no effect.
When the video showed an un-familiar chimpanzee yawning, there was no detectable effect amongst the subjects.
Contagious yawning is thought to be based on the capacity for empathy. Contagious yawning in chimpanzees provides further evidence that these apes may possess advanced self-awareness and empathic abilities.
Read More at Plos One