Kawamoto et al. (2013)

Kawamoto, T.(川本 大史), Michiru, A. (荒木 満瑠), & Ura, M. (浦 光博) (2013).
When a smile changes into evil: Pitfalls of smiles following social exclusion.
International Journal of Psychological Studies, 5(3), 21-27.
doi: 10.5539/ijps. v5n3p21
People have a fundamental and a critical need to belong. Social exclusion impairs this need and rejected individuals must seek to regain acceptance from others. It is known that such individuals show an increased preference for smiles. On the other hand, social exclusion sometimes leads to aggression. It is possible that this contradiction is modulated by acceptance and the level of control, such that prosocial behavior occurs in response to evidence of social affirmation, whereas aggression increases in response to reductions in the level of control. However, little is known about the impact of smiles without social affirmation, or the interaction between the effects of smiles and the level of control. In this study, we investigated the effects of such smiles by manipulating an excluder’s facial expressions (i.e., neutral and smiling faces) and similarity to the participant (i.e., level of control). We hypothesized that smiling excluders that are similar to the participant would increase aggression in the participant, presumably because being rejected by a similar partner reduces the level of control. In support of our hypothesis, results indicated that when excluders smiled, increased aggression was directed at those excluders that were similar to the participant. Our findings imply that a smile of an excluder directed at the person being excluded is one of the risk factors for aggressive behaviors in the excluded person.