Taste-induced facial expressions are thought to reflect the hedonic valence of an animal’s gustatory experience. We therefore assessed taste-induced facial responses in six black-handed spider monkeys (Ateles geoffroyi) to water, sucrose, caffeine, citric acid and aspartame, representing the taste qualities sweet, bitter, and sour, respectively. We decided not to include salty-tasting substances as the concentrations of such tastants found in the fruits consumed by spider monkeys are below their taste preference threshold. We found that the monkeys displayed significant differences in their facial responses between substances, with significantly higher frequencies of licking, sucking, closed eyes, tongue protruding, mouth gaping and lip smacking in response to sucrose, a presumably pleasant stimulus. The response to caffeine and citric acid, in contrast, yielded the lowest frequencies of these behaviors, but the highest frequency of withdrawals from the stimulus, suggesting these substances are perceived as unpleasant. Lip stretching, a newly described behavior, was performed significantly more often in response to caffeine than to any other substance, suggesting an association with the response to bitter taste. The facial response to the artificial sweetener aspartame was generally similar to the response to water, corroborating the notion that Platyrrhines may be unable to detect its sweetness. Overall, the present study supports the idea of similarity of taste-induced facial responses in non-hominoid primates and humans, suggesting these displays to be evolutionarily conserved across the primate order.

味觉诱发的面部表情被认为反映了动物味觉体验的享乐效价。因此，我们评估了六只黑手蜘蛛猴（Ateles geoffroyi ）的味觉诱导面部反应。) 到水、蔗糖、咖啡因、柠檬酸和阿斯巴甜，分别代表甜、苦和酸的味道品质。我们决定不包括咸味物质，因为在蜘蛛猴食用的水果中发现的此类促味剂的浓度低于它们的味觉偏好阈值。我们发现猴子在不同物质之间的面部反应表现出显着差异，在对蔗糖（一种可能是令人愉快的刺激）的反应中，它们舔舐、吸吮、闭眼、伸出舌头、张开嘴巴和咂嘴的频率明显更高。相比之下，对咖啡因和柠檬酸的反应产生了这些行为的最低频率，但从刺激中退出的频率最高，这表明这些物质被认为是不愉快的。嘴唇伸展，一种新描述的行为，对咖啡因的反应比对任何其他物质的反应更频繁，这表明与对苦味的反应有关。对人造甜味剂阿斯巴甜的面部反应通常与对水的反应相似，这证实了桔梗可能无法检测到其甜味的观点。总体而言，本研究支持非类人灵长类动物和人类中味觉诱导的面部反应相似性的观点，表明这些表现在灵长类动物中是进化保守的。证实了桔梗可能无法检测到其甜味的观点。总体而言，本研究支持非类人灵长类动物和人类中味觉诱导的面部反应相似性的观点，表明这些表现在灵长类动物中是进化保守的。证实了桔梗可能无法检测到其甜味的观点。总体而言，本研究支持非类人灵长类动物和人类中味觉诱导的面部反应相似性的观点，表明这些表现在灵长类动物中是进化保守的。