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 situationssuggesting
a level of emotional awareness that only humans are thought to possessaccording
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 expressionsa
play face (relaxed mouth open), a fear grimace (bared-teeth
display), a screaming face, a long-range greeting (pant-hoot) or an expressionless
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.
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
Yerkes and the National Science Foundation funded Parrs study.