Behavioral researchers led by Lisa Parr, PhD, director of the Yerkes National Primate Research Center Cognitive Testing Facility and Chimpanzee Core, have found understanding chimpanzee facial expressions requires more attention to detail than researchers initially thought. Correctly interpreting the subtleties within chimpanzees' facial expressions may be key to understanding the evolution of human emotional communication.
According to Parr, "This discovery is an important step to help researchers recognize facial movements and understand why they are important. While some expressions, such as a playful look, can be identified using a single feature, other expressions, such as when a chimp bares his teeth, require looking at numerous characteristics within the face, including the eyes and lips."
This is similar to what researchers see in human emotional expressions. "Sometimes it's easy to read what people are feeling, but at other times, we have to look at multiple places on their faces. Ultimately, we want to better understand what people are feeling and expressing emotionally because it helps us empathize with one another," Parr continued.
To facilitate her studies, Parr developed the Chimpanzee Facial Action Coding System (Chimp FACS) to directly compare documented expressions of humans and chimpanzees. Using Chimp FACS, the chimpanzees in the study observed anatomically correct 3D animations of chimpanzee facial expressions and then were asked to match the similar ones. "After the chimpanzees matched similar images, we separated individual features of the original animated expression, such as a raised brow, by frame and pieced the frames back together to create a variation of the original expression. The chimpanzees then were asked to match the new expression to the original one. This is how we determined when the chimpanzees were using a single feature or if they needed more than one feature to match the similar expressions," said Sheila Sterk, a senior animal behavior management specialist on Parr's team.