Exaggerating Facial Expressions: A Way to Intensify Emotion or a Way to the Uncanny Valley?

Exaggeration of facial expressions is used in animation and robotics to intensify emotions. However, modifying a human-like face can lead to an unsettling outcome. This phenomenon is known as uncanny valley. The goal of this study was to identify the realism level and magnitude of facial expression that produce the maximum amount of emotional intensity and the minimum amount of perceived strangeness. We studied the perceived intensity of emotion and perceived strangeness of faces with varying levels of realism (from schematic to photorealistic) and magnitude of facial expressions (from neutral to extremely exaggerated). We found that less realistic faces required more exaggeration to reach the emotional intensity of a real human face. While there is a range of emotional intensity that can be expressed by real human faces (from neutral to full intensity), we found that the same range of emotional intensity could be expressed by artificial faces when exaggeration was used. However, attempts to express emotional intensities outside this range using exaggeration led to strange-looking faces at all levels of realism.