Moraes Junior, F. P. (2019). Effects of Action Units, personality, and sociosexuality on perceptions of Duchenne and non-Duchenne smiles regardless attractiveness, health and feminity-masculinity. Perception of smiles is given by the characteristics of the decoder and the encoder. Action Units configure structure of each type of smile sent by the encoder. The encoder can use smile for various functions, such as expressing emotions or modulating nonverbal communication. Decoder, on the other hand, processes smiles through cognitive biases inherent in gender, personality, sexuality and other characteristics. Overall, Duchenne smile was shown to be considered as more attractive, healthy and feminine than social smile and neutral face. Moreover, faces with any kind of smile have also been rated more positively on these characteristics than the neutral face. The main objective of the present study is to test for possible differences between Duchenne, Social and Cheek Puffer smiles regarding perceived attractiveness, health and femininity-masculinity. The secondary objective is to verify whether personality and sociosexuality of the decoder have effect on smile evaluation. We hypothesized that Duchenne smile would be rated as the most attractive, healthy and feminine. Further, neuroticism, extroversion and more unrestricted sociosexuality were expected to have an effect on more positive evaluation of Duchenne smile compared to social smile. In total, 810 participants (58% women) were recruited online to rate 90 photos of their preferred sex. Standardized facial photos were taken from an online Brazilian database. Each rater judged photos with the three types of smiles and their corresponding neutral faces. They also filled in Big Five personality inventory (ICGF-5) and revised sociosexuality scale (SOI-R). Duchenne smile was rated as the most attractive, healthy and feminine in women and masculine in men. Cheek Puffer smile was evaluated more negatively on these characteristics. Extroversion, neuroticism and sociosexual behavior had little effect on differenciation between Duchenne and social smile. These results show that individuals are sensitive to different types of smiles, perceiving Duchenne smile as more positive because this smile is the most sociable and honestly signalizes happiness. Supposedly through the Hallo Effect, this smile was also perceived as the healthiest. Neuroticism and sociosexual behavior increase men's perceptual accuracy, and thus leads to higher sensitivity to emotions and signs of socialization. This is the first study to compare Duchenne smile with two other types of non-Duchenne smiles, showing these three types of smiles are functionally different. Thus, smile is a good model for demonstrating different functions of nonverbal behaviors that may look similar. Since smile is one of the most studied nonverbal behaviors, it demonstrates how little we still know about the functions of different non-duchenne smile types. We believe that this study brings a significant contribution to the area...