Moral identity in relation to emotional well-being: a meta-analysis.

Introduction: This meta-analytic review surveyed previous empirical studies that examined links between moral identity and indicators of emotional well-being. Additionally, this meta-analysis examined cultural origin as a moderator, testing if links between moral identity and emotional well-being differ in collectivistic vs. individualistic countries. Methods: A systematic literature review was conducted through ProQuest's 65 databases and PubMed. A random-effect meta-analysis and subgroup analyses were conducted using Comprehensive Meta-Analysis 4.0 (CMA) software. Results: Drawing on 27 eligible studies, moral identity was associated with greater emotional well-being (r = 0.27, p < 0.001). Follow up analyses on individual dimensions showed medium effect sizes in links between moral identity and greater happiness or positive affect (r = 0.28, p < 0.001), greater sense of purpose or meaning in life (r = 0.29, p < 0.001), and higher self-esteem (r = 0.25, p < 0.001). Moreover, moral identity was associated with greater life satisfaction showing a small effect size (r = 0.15, p = 0.011). Results showed that effect sizes of links between moral identity and overall emotional well-being did not significantly differ by cultural origin. However, effect sizes tended to be larger in the nine studies that were conducted in collectivistic countries (r = 0.30, p < 0.001) as compared to the 15 studies that were conducted in individualistic countries (r = 0.27, p < 0.001). Discussion: The results of this meta-analysis indicate a robust empirical relationship between moral identity and emotional well-being that is present across various dimensions of emotional well-being and in both individualistic and collectivistic cultures. Systematic review registration: https://osf.io/94f8b/?view_only=6db54da0fa304c83993d0438ecb5c637.

European starlings are capable of discriminating subtle size asymmetries in paired stimuli.

Small deviations from bilateral symmetry (fluctuating asymmetries) are cues to fitness differences in some animals. Therefore, researchers have considered whether animals use these small asymmetries as visual cues to determine appropriate behavioral responses (e.g., mate preferences). However, there have been few systematic studies of animals' abilities to visually discriminate such minor asymmetries. If the asymmetries cannot be discriminated, fluctuating asymmetry can not be a visual cue. Here, we report an investigation of European starlings' (Sturnus vulgaris) abilities to discriminate small size asymmetries. We trained starlings, through operant conditioning in a free-flight aviary, to discriminate achromatic, symmetric paired stimuli from size-matched asymmetric stimuli. By starting the learning process with a large asymmetry and progressing through sequential trials of decreasing asymmetry, we elucidated a behavioral limit to asymmetry discrimination. We found that starlings are capable of discriminating a 10% size asymmetry. There was weaker evidence for discrimination of 5% asymmetry but no evidence for signal discrimination at 2.5% size asymmetry. This level of asymmetry discrimination suggests that many size asymmetry cues in nature can be discriminated by birds. At each level of asymmetry discrimination, we also tested whether starlings could generalize their learned symmetry preference to unreinforced novel images. Consistent with previous findings, we found that starlings could generalize their symmetry preferences.