We also examined the effect of relationship between recipient and benefactor on three feelings of gratitude and enhancement of prosocial motivation in each sample. The findings reveal that both high school and undergraduate students reported more feelings of appreciativeness in case that father, mother and teacher, rather than friend, provided help. In addition, they reported more enhancement of prosocial motivation in case that mother and father, rather than teacher and friend, provided help. This finding was contrary to the previous research concerning the effect of relationship on gratitude (Bar-Tal et al., 1977). This result presumably was caused by people who appear to feel more grateful when they received a favor from a benefactor who is social superior such as parents or teachers, than a favor rendered by a person of similar social status (Hegtvedt, 1990). Also, the characteristic of gratitude be operated in this study that described feelings of appreciativeness was linked with the concept of respect. Thus, Thai students feel more appreciated with their parents and teachers, than friends who hold equal social status. These characteristics of gratitude in Thai adolescents were consistent with the concept of gratitude by Kant (2012). According to Kant (2012), gratitude consists of the feeling of respect for the benefactor. Gratitude is a duty which cannot rid oneself of the obligation for repayment a kindness received. A grateful disposition of this kind is called appreciativeness. In addition, the finding that students reported more prosocial motivation in father and mother than friend might be assumed that feelings of appreciativeness, which based on respectfulness significantly, enhance prosocial motivation. However, the certain evidence for this assumption is still insufficient.