We describe an experimental Collaborative Problem-Solving (CPS) environment involving computer-mediated communication (CMC), that is designed to favour the production of argumentative interactions and to enable the cognitive changes that they produce to be modelled. Our approach is based on defining a restricted set of psychological and logico-linguistic conditions for generation of argumentation, an original algorithm for optimising constitution of dyads for critical discussion and a computer-based environment that combines graphical and language-based problem-solving with CMC discussion. This approach enables us to study learners' solutions, justification structures and attitudes, before and after CPS activity, and thus to assess the role of argumentative interactions in students' changes in view. Corpus analysis showed that whilst the environment is successful in favouring argumentative interactions, it leads to increased awareness in students concerning the nature of their problem-solving task (in this case, modelling energy in physics) rather than an improvement in solutions or conceptual understanding.