Meng et al. (2019)

Meng, X., Ishii, T.(石井辰典), Sugimoto, K., Song, R., Moriguchi, Y., & Watanabe, K. (2019)
Smiling enemies: Young children better recall mean individuals who smile
敵対者の微笑み:5-6歳児は "微笑んだいじわる" の顔をよく記憶する
Journal of Experimental Child Psychology,188 
Remembering whether a person is cooperative is essential in social interactions. It has been shown that adults have better memory of a person who showed an incongruence between emotional expression and expected behavior (e.g., smiling while stealing). To examine whether children would show similar emotional incongruity effects, we examined 70 children between 5 and 6 years of age. They obtained coins that could be exchanged later for rewards (stickers) by answering quiz questions. Then, they participated in the coin-collecting game wherein individual persons with smiling or angry expressions appeared one at a time on a computer monitor. These same individuals then either gave coins to or took them away from the children, leading to congruent (smiling giver and angry taker) and incongruent (smiling taker and angry giver) conditions. After the game, children had to choose between two faces to indicate which one previously appeared in the game. Participants recognized faces better under the incongruent conditions. In particular, the smiling taker was recognized significantly better than the angry taker, whereas no difference was observed for the smiling and angry givers. Evidently, 5-to-6-year-old-children remember better individuals whose facial expression or appearance is incongruent with their expected behavior.