Group Decision-Making (GDM) problems usually include stakeholders with different views and opinions. In order to find a collective solution, it is necessary to achieve a Consensus Reaching Process (CRP) that may lead to the emergence of non-cooperative behaviors within the group. This paper proposes to study how these non-cooperative behaviors appear in a group of decision-makers and what their level of impact is on the evolution of consensus and on the final decision. To provide some answers to this research problem, we propose a Multi-Criteria Decision-Making (MCDM) methodology implementing AHP (Analytic Hierarchy Process) in order to provide a visualization of the CRP evolution and observe four non-cooperative behaviors within small-scale group decision-making: 1-Collective agreement, 2-Blocking Behavior, 3-Leadership demonstration and 4-Experts' coalition. We implement our methodology within a pedagogical framework, in 29 small-scale groups of Masters and engineering students, through a case study related to the implementation of forest management scenarios in France. Our results show the evolution of the four non-cooperative behaviors within the groups, as well as their impact on the CRP outcomes.