chimpanzees sorrowful countenance hints at its underlying feelings of sadness and dejection

social media facebook post instagram size mobile chimpanzees sorrowful countenance hints underlying feelings sadness dejection primate emotions facial expressions animals communication nonverbal behavior empathetic psychology empathy expression primates perception body language cues evolutionary biological cognitive instinctive mournful melancholy dejected gloomy somber crestfallen unhappy despondent disheartened