Faces fascinate. Babies love them. We look for familiar or friendly ones in a crowd. And video game developers and movie animators strive to create faces that look real rather than fake. Determining how our brains decide what makes a face "human" and not artificial is a question Dr. Benjamin Balas of North Dakota State University, Fargo, and of the Center for Visual and Cognitive Neuroscience, studies in his lab. New research by Balas and NDSU graduate Christopher Tonsager, published online in the London-based journal Perception, shows that it takes more than eyes to make a face look human.
Researchers study the brain to learn how its specialized circuits process information in seconds to distinguish whether faces are real or fake. Balas and Tonsager note that people interact with artificial faces and characters in video games, watch them in movies, and see artificial faces used more widely as social agents in other settings. "Whether or not a face looks real determines a lot of things," said Balas, assistant professor of psychology. "Can it have emotions? Can it have plans and ideas? We wanted to know what information you use to decide if a face is real or artificial, since that first step determines a number of judgments that follow."
Results of the study show that people combine information across many parts of the face to make decisions about how "alive" it is, and that the appearances of these regions interact with each other. Previous research suggests that eyes are especially important for facial recognition. The NDSU study found, however, that when you're deciding if a face is real or artificial, the eyes and the skin both matter to about the same degree.
Balas and Tonsager, as an undergraduate researcher in psychology, recruited 45 study participants who were evaluated while viewing altered facial images. Tonsager cropped images of real faces so only the face and neck showed, without any hair. A program known as FaceGen Modeller was used to transform the images into 3D computer-generated models of faces. Photos were then computer manipulated into negative images. In two experiments, transformations to real and artificial faces were used to determine if contrast negation affected the ability to determine if a face was real or artificial, and whether the eyes make a disproportionate contribution to animacy discrimination relative to the rest of the face.
"We assumed that the eyes were the key in distinguishing real vs. computer generated, but to our surprise, the results were not significant enough for us to conclude this," said Tonsager. "However, we did find that when the skin tone is negated, it was more difficult for our participants to determine if it was a real or artificial face. The research leads us to conclude that the entire 'eye region' might play a substantial role in the distinction between real or artificial."
"Beyond telling us more about the distinction your brain makes between a face and a non-face, our results are also relevant to anybody who wants to develop life-like computer graphics," explained Balas. "Developing artificial faces that look real is a growing industry, and we know that artificial faces that aren't quite right can look downright creepy. Our work, both in the current paper and ongoing studies in the lab, has the potential to inform how designers create new and better artificial faces for a range of applications."
Balas and Tonsager also presented their research findings at the Vision Sciences Society 13th Annual Meeting, May 16-21 in St. Peterburg, Florida.
The research study of Balas and Tonsager was funded by North Dakota Experimental Program to Stimulate Competitive Research NSF #EPS-0814442 and Center of Biomedical Research Excellence Grant GM103505 from the National Institute of General Medical Sciences (NIGMS), a component of the National Institutes of Health (NIH).
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