Görkem Er¹ (), Timothy D. Sweeny¹; ¹University of Denver

Perception of facial expressions is highly contextual. For example, when an individual face is seen around other faces, people tend to say its expression looks like the others in the crowd. However, this effect of perceptual averaging has only been shown when faces are static and perceivers must attend to many faces at once. Here we examined (1) whether this effect persists in more rich and realistic contexts, when faces are dynamic and attention can be biased to a single face in a crowd. Additionally, when a face is dynamic, perceivers may overestimate its emotional intensity in the direction of its changing expression (e.g., perceiving the expression at an intensity it appears to be heading towards rather than its actual intensity), which we refer to as expression-trajectory bias. We examined (2) whether crowds exaggerate this effect. Observers rated the emotional intensity of a target face that appeared at a random location, dynamically expressing increasing or decreasing intensities of anger or happiness for 333-ms. This target face appeared among three non-target faces, which transitioned from neutral to full expressions of happiness or anger across 1,666-ms. We found two distinct effects of the dynamic crowd context on ratings of individual’s expressions. First, ratings were pulled towards the emotion of the crowd; angry faces appeared less intense among happy crowds and happy faces appeared less intense among angry crowds. Second, we found clear evidence of expression-trajectory bias in judgments of individuals' dynamic expressions. This bias, however, was mitigated in the context of crowds. Crowds may thus serve as a reference when judging an individual’s dynamic expression. These two simultaneously occurring effects extend prior findings, demonstrating that contextual effects in the perception of facial expression can occur when faces are dynamic and even when selective attention is engaged.