H. Robert Quilitch’s research while affiliated with University of Nevada, Reno and other places

... Research on cooperative gameplay in both video games and non-video game settings has demonstrated positive and beneficial effects on players. Early studies have shown that playing games cooperatively fosters cooperative and sharing behaviors, reduces aggression, and increases positive communication and prosocial behaviors among children (Bay-Hinitz et al., 1994;Garaigordobil et al., 1996;Iplikci et al., 2024;Orlick, 1981;Street et al., 2004). Likewise, in video game settings, cooperative gameplay was reported to decrease aggressive behaviors and attenuate aggression after violent video game playing (Jerabeck & Ferguson, 2013;Velez et al., 2016). ...

Reference:

Competition and Cooperation in Video Games