She and her team observed 22 sun bears in their forested enclosures, recording more than 370 different play bouts on video. The researches then pored over the footage, meticulously evaluating and tallying differences in the bears’ facial expressions and their timing.

The bears would often open their mouths towards their play partner in one of two ways, either with the teeth exposed or hidden under the lips. The researchers found that the bears were predominantly producing either of these open-mouth expressions when they saw their play partner was looking at them. Changing a facial expression when given attention by someone else, until now, was only known in primates and dogs—the latter of which shares a life with, and has been domesticated by, humans.

When met with an open-mouthed signal, most of the bears would copy the expression right back, often within one second of seeing the expression. This “rapid facial mimicry,” also had only been seen in primates and dogs.

Most interestingly, the copycats reproduced an exact match of their partner’s chosen face, not just throwing out any old open-mouthed mug. This precise expression matching was thought to be the domain of humans and gorillas only, so bears trying it out is completely new.