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August 6, 2001

Parr learns chimpanzees can second that emotion

By Poul Olson


Chimpanzees recognize the emotions in facial expressions presented in a video and respond physiologically to emotionally stressful situations—suggesting a level of emotional awareness that only humans are thought to possess—according to a study reported in the journal Animal Cognition by Lisa Parr, a postdoctoral fellow in psychobiology at Yerkes Primate Research Center.

Parr tested three chimpanzees that previously had been trained to use a computer joystick to match similar facial expressions. She showed the animals brief, videotaped scenes of other chimps being injected or darted during routine veterinarian procedures.

The subjects then used the joystick to match these scenes with photographs of other unfamiliar chimpanzees displaying one of five facial expressions—a “play” face (relaxed mouth open), a fear grimace (bared-teeth display), a screaming face, a long-range greeting (pant-hoot) or an expressionless face (neutral).

After viewing the videos, the chimps consistently matched the “negative” scenes of the chimpanzees undergoing injections with the photographs of screaming or bared-teeth expressions.
In contrast, when Parr presented them with “positive” images, such as scenes of favorite foods and the computer-testing apparatus, the chimps matched them with the play-face image. Correct responses were rewarded with a squirt of grape juice; incorrect responses were not.

“Chimpanzees clearly have an ability to represent emotion at a higher cognitive level than we have suspected,” Parr said. “What has yet to be demonstrated is the degree to which they gain emotional information from their facial expressions or perceive basic categories of emotion.”

In another experiment, Parr measured skin temperature changes in the chimpanzees’ left middle fingers while they watched others being injected. Videos of darts and needles alone also were presented.

Parr found that skin temperature decreased rapidly in response to the negative video scenes. This physiological change is similar to what humans experience when they feel fear or sadness.

Noting the traditional resistance to the notion that animals feel emotion, Parr said that researchers have attempted to quantify emotional responsiveness in nonhuman primates. Her study is the first to suggest that chimps have emotional awareness and can derive “symbolic” emotional meaning from social signals like facial expressions.

Parr was particularly intrigued by the chimps’ physiological response to seeing others in distress. She believes that this may be similar to empathy. This process would enable chimpanzees to transmit emotional information to each other in passive, but meaningful ways.

“This discovery has important evolutionary implications,” Parr said, “given that the ability to understand emotion in others is one of the most significant factors involved in regulating social interactions in humans.”

Yerkes and the National Science Foundation funded Parr’s study.


Back to Emory Report August 6, 2001