Point-light displays can tell us an amazing amount about other people. Looking only at a few glowing spots corresponding to joints and set in motion, we can tell what people are doing, whether they are over- or underweight, and even identify a friend among strangers. We can also identify animals or determine the emotional state a dancer or actor is conveying. But some emotions are more difficult than others. Take a look at the following two animations (click on the image to view a quicktime movie):
Now, which emotion does each animation convey? Your choices are Anger, Joy, Sadness, Love, Fear, or Disgust. You can post your guess in the comments section, and we’ll let you know when someone gets it right.
These figures came from an experiment conducted by Tanya Clarke and several colleagues (you can visit the Perception web site to see more examples, but be prepared for a long download!). They had several different actors perform the same scene but conveying different emotions (you may have seen comic Colin Mockery doing this same thing — to hilarious effect — on the improvisation TV show Whose Line Is It, Anyway?). The actors were allowed to repeat the scenes until they believed they conveyed the emotions adequately. Participants viewed the scenes as silent point-light displays, then rated them for how well they conveyed each of the emotions in the list. Here are the results:
As you can see, the viewers had little trouble with this task. When actors were portraying anger, for example, the participants rated the point-light displays as 70 percent effective in conveying anger, but all the other emotions averaged less than a 20 percent rating. The difference between the intended emotion and other emotions was significant in every case.
Next, the same viewers saw the same displays inverted — upside-down. This time, the results were less consistent:
While viewers were still able to recognize anger, joy, sadness, and love, the two other emotions — fear and disgust — were rated as highly for other emotions as they were for the intended emotions.
Next Clarke et al. designed a new experiment to test what aspects of the displays were critical for expressing emotion. They generated two new types of animation — one where one of the actors was cropped out of the picture, and another where instead of two actors interacting, the display was a reflection of the same actor’s image. Here are the results:
For anger, joy, and sadness, each display was equally effective at expressing the intended emotion. However, when attempting to express love, one actor alone was significantly less effective compared to two actors together. Viewers even rated the reflection of the identical actor to create two “people” as expressing love. Love, it appears, requires two people in order to be displayed effectively, but those two people needn’t actually be interacting in a meaningful way. For fear, people rated the reflected image as less effective than the other displays. So fear appears to require one person reacting to another, or one person alone.
Perhaps the most important finding of this study is how often emotion can be conveyed with point-light displays, and how versatile the visual system is at perceiving emotion. Out of 27 types of point-light displays across two experiments, only four failed to express the desired emotion.
One more note: a tremendous resource for playing with point-light displays is the BioMotionLab. If you haven’t tried this tool before, you should definitely give it a whirl. You can even create your own custom point-light display conveying any emotion or body type you desire.
Clarke, T.J., Bradshaw, M.F., Field, D.T., Hampson, S.E., & Rose, D. (2005). The perception of emotion from body movement in point-light displays of interpersonal dialogue. Perception, 34, 1171-1180.