This paper describes the findings of an experimental research concentrating on collaboration in a multi-player video game. The overall goal is to study the cognitive impacts of the awareness tools. The focus is in finding an effect on performance as well as on the representation an individual build of what his partner knows, plans and intends to do (i.e. Mutual Modelling). Using an awareness tools has a significant effect by improving task performance. However, the players who were provided with this tool did not show any improvement of their mutual modelling. Further analysis on contrasted groups revealed that there was an effect of the awareness tool on mutual modelling for players who spent a large amount of time using the tool.