Because humans use verbal language to communicate, we often don’t notice all the subtle nonverbal cues we give off during interactions with others. Working directly with another species definitely makes you notice those cues, both in nonhuman animals and in humans. Sometimes if someone misinterprets what you are saying or doing, you have to almost exaggerate the opposite cues to make sure they don’t keep thinking you were purposely being mean.
An easy example is when dogs are playing, and if one dog starts to think things are becoming more aggressive, they may snarl and bark and seem somewhat threatening. If the other play partner wants to make sure things don’t get out of control, they will play bow really low to the ground, wag their tail with enthusiasm, and make sure their teeth are not bared. The opposite cues are standing tall, hair up, and teeth bared, and that is how they show aggression. The same can be said for chimps, as well. They have opposite cues for opposite circumstances. When trying to be aggressive, they stand up, swagger, pant hoot, and show all their top teeth to demonstrate how intimidating they are. Opposite behaviors are bowing down, showing a play face (hiding their top teeth), bobbing their head, laughing, and so on to show they are being playful.
Sometimes play can get kind of exciting, and there is a fine line between play and threat. The other day I was playing with Foxie and we were stomping and she was hitting the ceiling. Though she was definitely playing with me, Negra couldn’t see Foxie’s play face and misinterpreted her actions as a threat. Negra started to swagger and pant hoot and her hair was standing up a bit. Foxie quickly wanted to let Negra know she was not at all being aggressive and so she was extremely exaggerated in her play behaviors. She approached Negra with a low posture and really big play face, laugh, and playfully slapped the ground. Negra understood what was going on and began to chase Foxie across the loft and the catwalk of the playroom (at Neggie speed, of course) and I was able to catch the tail end of this play session. You can see how Foxie is continuing to use everything in her arsenal to make sure Negra knows she means to be playful.