The visual nature of social interaction and its impact on overall mood judgments

Humans can rapidly assess a crowd's overall mood, allowing socially adaptive behaviour. Prior work suggests that an interacting individual's emotional judgment is shaped by the facial expressions of their interaction partner. However, research has yet to systematically investigate how social interactions - and the visual cues signaling them - influence judgments of overall mood in naturalistic scenes. To address this, we examined the visual nature of social interaction and its role in evaluating crowd mood. Using natural photographs of groups (over five people) either interacting or not, we manipulated visual cues such as context, facingness, and mutual gaze. Participants judged the degree of social interaction and the overall mood among the people in photographs. A deep learning algorithm was used to estimate the emotional intensity of the images. Across five experiments, participants utilised social cues when evaluating a crowd's overall mood. Crowds engaged in social interaction were judged as more positive and as having greater sensitivity to positive emotion than non-interacting crowds. However, perceived social interaction, bias, and sensitivity gradually decreased as these social cues were removed. These findings highlight the importance of social visual cues in mood perception and suggest that humans intuitively integrate social context to interpret group emotions.