In the context of collaborative interaction analysis, we have to deal with our team-mates share the context in which they carry out their joint activity. Collaboration indeed requires intersubjectivity: the understanding of another person depends on the assumptions the observer can make about what hes understanding and planning. Carrying out a joint activity depends on this intersubjectivity: a mutual and shared understanding based on the immediate experience of two persons who have only access to their own thoughts and the actions performed by each of the participants This notion of mutual intelligibility has been extensively studied by scholars, it is called: - 'mutual knowledge' by philosophers specialised in language studies: Smith 1982 or Grice, 1975 - 'common ground' by psycholinguists: Clark, 1991 or 'mutual knowledge' by Krauss and Fussel, 1990: they claim that communication needs a common ground, a common body of knowledge between interactants. - 'shared cognitive environment' by Sperber and Wilson, 1986: unlike Clark, they states that communication is just the intersection between different individual cognitive environment/context.