Emotion and the perception of biological motion

As an organ designed to produce contextually dependent behaviors that are, on average, adaptive, we should expect the brain to bias perception to facilitate a flight response in a dangerous situation. In humans, adaptive perceptual biases have been demonstrated for slant, height, and sound amplitude. We hypothesized that the human visual system is biased to perceive others as being quicker and angrier when approaching the observer in a fearful situation. Two studies examined the effect of fear on biological motion perception. In experiment one, participants who viewed high-arousal picture sets from the IAPS library perceived motion capture wireframes as moving more quickly than participants who viewed low-arousal sets. In experiment two, participants wrote about either a happy or frightening memory. Those who reported feeling frightened during the recall perceived the wireframes as moving faster when the wireframe was approaching the participant. Males in the study perceived wireframes as angrier when approaching, and more scared when moving away than did females in the study. Nervousness produced a strong effect on speed and anger in both directions. The results support the hypothesis that biological speed perception is adaptively biased by fear, but perceived anger was not. Interestingly, males appear to see people approaching them as angry, and those moving away as afraid, suggesting that males sort others into threat categories based on observed movement. The surprising role of nervousness in the perception of biological motion may indicate that, in states of uncertainty, the brain assumes the worst