This paper presents a method for monitoring mental state of small isolated crews during long-term missions (such as space mission, polar expeditions, submarine crews, meteorological stations, and etc). It combines the records of negotiation game with monitoring of the nonverbal behavior of the players. We analyze the records of negotiation game that has taken place between the crew members who were placed in isolated environment for 105 days during the Mars-500 experiment. The outcomes of the analysis, differently from the previously made conclusions, show that there was not a significant deviation of the rational choice of the players. We propose an extension of the method that includes monitoring of the nonverbal behavior of the players next to recording the game records. The method is focused on those aspects of psychological and sociological states that are crucial for the performance of the crew. In particular, we focus on measuring of emotional stress, initial signs of conflicts, trust, and ability to collaborate.