How Does More Niceness Bring More Happiness? The Association Between Niceness, Depression, and Subjective Happiness

Behavioral niceness has an important place in maintaining interpersonal relationships. Scale studies are needed to determine the level of niceness that plays a role in individuals' development of healthy daily interactions with other people. In this study, firstly, the psychometric properties of the Niceness Scale, which consists of six items, were examined in a Turkish sample (<i>N</i> = 404). Confirmatory factor analysis confirmed the six-item one-dimensional structure, and item response analysis revealed a high level of discrimination across all items. The relationship of the Niceness Scale with previously validated and reliable scales was examined, and it was found that criterion-related validity was achieved. Furthermore, a network analysis revealed the relationships between the variables more clearly. In the scale's measurement invariance analysis, consistency was found for both genders. Then, the reliability of the Niceness Scale was proven with different reliability values. In a different Turkish sample (<i>N</i> = 372), it was determined that depression played a statistically significant mediating role in the relationship between niceness and subjective happiness. In conclusion, this study revealed that the one factor and six-item Niceness Scale are valid and reliable in the Turkish sample. Moreover, boosting niceness has been determined to reduce negative situations such as depression and therefore enhance subjective happiness. All these important implications about niceness are discussed in light of the literature.