The goal of this research was to investigate contribution of organized youth sport to prosocial orientation, morality and aggressiveness in high school students, and to determine the possible moderator effect of gender and type of sport (individual/group) on this relationship. Current research related to participation in sport and moral and social development of young people has unclear and contradictory results (Gasic-Pavisic & Janjetović, 2007; Endersen & Olweus, 2005; Lai, Stoll & Beller, 2006). The first group of research supports the view that dealing with sports can increase the aggression and antisocial behaviour of young people (Gašić-Pavišić & Janjetović, 2007, Visek et al, 2010), in the sense that sport represents a context in which models of aggressive behaviour are presented, aggressive behaviour is expected and therefore encouraged and rewarded (Vidanovic, Bisercic, Andjelkovic, 2013). Endersen and Olweus (2005) founded that participation in power sports leads to an increase or reinforcement of the antisocial and violent behaviour of boys outside sports. Some studies showed lower development levels of morality for athletes than for nonathletes (Jones, 2005; Lai, Stoll & Beller, 2006). The second group of studies on adolescent confirmed that fostering moral thinking in a sporting context can improve the prosocial behaviour of young sportsmen (Rutten et al., 2007; Jones et al, 2011).

An overview of empirical studies highlighted the possibility of various effects of sports on boys and girls. Rutten et al. (2007) found that women's teams have a higher level of moral functioning than men's, lower levels of approval of unsportsmanlike behaviour and less inclination to hurt rival in sports. Popadic et al. (2011) also found that aggressive behaviour is more represented among sportsmen than among sportswomen. Gasic-Pavisic and Janjetovic (2007) found a significantly lower level of manifestation of prosocial orientation and lower expressed aggressiveness in girls when they compared sportswomen with sportsmen.

Researches by some authors (Coulomb-Cabagno & Rascle, 2006, Maxwell & Moores, 2007) have shown that there is a higher degree of aggression and the approval of unsportsmanlike behaviour in individual sports, especially those in which greater physical contact is present, for example boxing and judo.

Bearing in mind the contradictory results of previous researches, the main aims of this study were: (1) To examine the degree of manifestation of prosocial behaviour, morality and aggressiveness at high school athletes in relation to nonathletes; (2) Examine the moderation effects of gender on this relationship; (3) Examine the differences between team and individual sport athletes in prosocial orientation, morality and aggressiveness

The sample consisted of 150 respondents, 75 sports-students (37 girls and 38 boys) and 75 non-sports-students (37 girls and 38 boys), high school students in Prokuplje, average age 16.02 (SD =0,984) years. Instruments: The Questionnaire about sport activities (Gasic-Pavisic & Janjetović, 2007): regular participation in sports activities, i.e. dealing with certain sports (yes or no); time period of active sport participation (up to a year, a year, more than a year); number of trainings per week (a week, several times a week); type of sport (individual or team) and which sport precisely. The Scale of Altruism (Raboteg-Saric, 1993), it’s made of 17 items in the five-point Likert scale. The task of the respondents was to assess how much the claims relate to them, where 0 means "never" and 4 means "very often". Altruism was defined as a special form of peer education. It involves action that doesn’t encourage a social prize or avoidance of punishment, but is encouraged to improve or maintain such well-being (Raboteg-Saric, 1993). Interpersonal Reactivity Index (Davis, 1983). The questionnaire contains 28 items divided into 4 subcategories with 7 sub-items in all subcategories. Two subscales cover the domain of emotional empathy (empathic care and personal uneasiness), and two cognitive empathy (taking on another's point of view and fantasy). The task of the respondents was to determine on the five-step scale of Liker’s type. Modified Moral Competency Inventory ‒ MCI (Lennick & Kiel, 2011). The final version of the inventory consists of 32 items distributed in the following way in the four sub-submissions that are used to examine four properties of the moral person: the integrity (12 items), compassion (7 items), responsibility (7 items) and forgiveness (6 items). The Basic aggressiveness questionnaire - SIGMA 4 (Momirovic et al., 1992). This questionnaire has been separated from the cybernetic battery of the conventional test of KON6 by Momirovic et al. (Momirovic, Wolf and Dzamonja, 1992). It is intended to evaluate the efficiency of the system for regulation and control of the reaction of attacks from the Cybernetic model of regulatory functions. The questionnaire contains 30 items (Likert's type).

Results showed that there was a positive correlation to sports involvement with the level of altruism (athletes showed a higher degree of altruism compared to nonathletes), as well as association between sporting activity and aggression, that is, young people who do not engage in sports show a higher level of aggression compared to those who are spot-active. However, it turned out that there is a moderate effect of gender on this relationship. In girls, dealing with sports is associated with a more pronounced tendency to forgive one's own and others' mistakes (one aspect of morality), while within boys it has reverse connection, i.e. nonathletes are more inclined to forgive than athletes. Two-factor ANOVA revealed interesting finding that there is a moderate effect of gender on the relation of sports and the expression of aggressiveness in the way that there is more aggressiveness in the female athletes than in female nonathletes, whereas in the young men this relationship is reversed, athletes are less aggressive than nonathletes. In accordance with the assumption, the results of two-factor ANOVA have shown that athletes who engage in individual sports are more aggressive than those who engage in team sports. Either more aggressive young people choose sports that have individual imposition and physical contact (a greater choice of sports), or engaging in these types of sports contribute to aggression through competition and encouraging aggressive behaviour (Endresen, Olweus, 2005). Also, athletes who train team sports have a more developed moral character - integrity than those who choose individual sports. Unfortunately, our research did not include trainers, but future research could explore their contribution to the moral and social development of young athletes.

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