The present research addresses the relationship between performance of sport teams and quality of the social ties among team members. Sport teams are considered as an instance of teamwork characterized by specific roles and common goals to achieve. Two relational dimensions of social ties are considered: professional relationships and friendship (the former captures how well team members can play together, the latter how often they meet each other outside training and competitions). In addition, the role of both positive and negative relationships is investigated. The analyses are conducted at the level of the match and the average indegree centrality of positive and negative ties among the players are used to predict the result of the match. Interestingly, the results differ between professional and non-professional teams. Among professional players positive ties influence positively the performance but negative ties have no effect. Conversely, in non-professional context (where athletes receive only a small economic compensation), negative ties influence the performance negatively but positive ties have no effects. The results differ between professional and non-professional also concerning the effects of professional and friendship ties: both types of ties affect the performance of professionals significantly while for non-professionals the effects are somewhat inconsistent.
Keywords: Network analysis, negative ties, cognitive social structure, sport teams, group performance