The Rich Emotional Lives of Chimpanzees and Goats

Studies of the emotional lives of numerous and diverse nonhuman animals (animals) consistently show that some humans wrongly underestimate what they're able to pick up from the behavior of other individuals. Two recent studies of chimpanzees and one on goats caught my eye because they reveal emotional capacities—emotional intelligence and emotional contagion—that show how emotionally aware individuals of these species truly are.

Let's consider chimpanzees first. A study published in the journal Primates by the University of Michigan's Rachna Reddy and John Mitani called "Social relationships and caregiving behavior between recently orphaned chimpanzee siblings" shows, "When their mothers die, chimpanzees often adopt younger vulnerable siblings who survive with their care." A second study by Kyoto University's Yutaro Sato and his colleagues published in Animal Cognition, "Spontaneous attention and psycho-physiological responses to others’ injury in chimpanzees," shows that chimpanzees understand when other chimpanzees are suffering and emotionally respond when they see that another chimpanzee, or a familiar human, is injured.

Michael Marshall provides an excellent summary of both studies in a piece called "Death of mother prompts adolescent chimps to look after their siblings." (None of these essays are available online for free, but the abstracts are and they're easy to summarize.) Reddy and Mitani were able to observe interactions between older chimpanzees and younger siblings at Ngogo in Kibale National Park, Uganda, after their mothers died from a respiratory disease that killed several females. They studied four adolescent and four young adults and were able to document their behavior toward immature younger maternal siblings before and after their mothers died. They write, "Following the death of their mothers, siblings increased the amount of time they associated, maintained spatial proximity, groomed, reassured, and consoled each other. During travel, younger orphans followed their older siblings, who frequently looked back and waited for them. Both siblings showed distress when separated, and older siblings demonstrated heightened vigilance in dangerous situations." They also were able to study how the behavior in four sibling pairs who were recently orphaned compared to 30 pairs of siblings whose mothers were still alive. They learned that recently orphaned siblings showed similar patterns of interaction—more than did those who mothers were still alive. Taken together, the results show that after mothers died, siblings helped one another along.

The nose knows. Sato and his colleagues' study was conducted on six captive chimpanzees. In their creative and novel research, they focused on how individuals responded to others who were injured. Using eye-tracking, they discovered, "Chimpanzees spontaneously attended to injured conspecifics more than non-injured conspecifics, but did not do so in a control condition in which images of injuries were scrambled while maintaining color information." They also used thermal imaging to measure the temperature inside the noses of the chimpanzees. Previous research had shown that reduced nasal temperature—a cold nose—is associated with negative emotions. When chimpanzees observed a prosthetic wound and artificial blood in a familiar human experimenter, they displayed colder noses than they did in a control situation. The researchers conclude, "These results suggest that chimpanzees inspect others’ injuries and become aroused by seeing injuries even without observing behavioral cues, but have difficulty doing so without explicit (or familiar) cues (i.e., open wound and blood)."

Both of these studies show chimpanzees are able to understand when others are in distress. I look forward to further studies of how chimpanzees and other animals share emotional states and how they respond to individuals in need. (Just as I was finishing this piece I saw an essay called "After This Young Monkey Got Hit by a Car, Monkey Strangers Comforted Him" that speaks to the results of these two studies.)

Goats can tell the difference between "happy" and "sad" vocalizations

Goats also figure into this discussion of shared emotions. In a study published in Frontiers in Zoology by Luigi Baciadonna and his colleagues called "Goats distinguish between positive and negative emotion-linked vocalizations," we learn that highly social goats display emotional contagion and are able to distinguish what others are feeling based on their calls. (This study is available for free online and not surprisingly, it's also covered in many mass media outlets.) The researchers recorded the vocalizations that goats made when they were assumed to be happy—being fed or when reuniting with others—and when they were assumed to be sad—watching others eat when they couldn't. The recordings were then played back to goats and the researchers studied their reactions. They learned that goats could distinguish between "happy" and "sad" calls and also responded physiologically. They paid more attention to "sad" calls that had negative valence than to "happy" calls. Heart rate was the same in both situations, but when they heard "happy" sounds, their heart rates were more variable. This appears to be the first study demonstrating emotional contagion and empathy via vocalizations. Renowned primatologist, Frans de Waal agrees: “Goats being sensitive to the emotions of others is a form of empathy. Empathy is a mammalian trait, so this makes sense.” (Also see "Why Sheep Matter: They're Intelligent, Emotional, and Unique.")

All of these studies show that chimpanzees and goats are sensitive to the emotional states of other individuals, and that their emotions might function as social glue. (See "Dog, Cats, and Humans: Shared Emotions Act As "Social Glue.") The results also have some bearing on questions about whether other animals display a Theory of Mind (ToM), or the ability to attribute mental states to oneself and others and understand that others have beliefs, desires, and perspectives different from one's own. There are data that strongly suggest they do. (See "Theory of Mind and Play: Ape Exceptionalism Is Too Narrow" and "Ravens Know They're Being Watched: Bird Brain Theory of Mind.")

Stay tuned for further discussions of comparative research on the emotional lives of other animals and what's happening in their active minds and hearts. This is a very exciting area of research. Many animals display emotional contagion and emotional intelligence, and this isn't all that surprising when one considers the sorts of cognitive and emotional capacities necessary for the evolution of social living.