In this study, we are more concerned with the early stages of the new product design: the product definition phase. The fundamental purpose of this phase is to gather right kind of information in a way that allows the formalization of stakeholder needs into a set of requirements. Literature review on this phase shows the difficulty to elicit needs of so called intended users and have a shared understanding of their requirements between design actors. To overcome these obstacles, support methods can be used. However, the appropriateness and effectiveness of the various methods is unknown. Our assumption in this research project is that scenarios and personas can be used as support methods to handle above-mentioned obstacles. An experiment is designed and conducted in a laboratory environment in order to test this assumption. The question of whether they have an impact on the creation of shared understanding between design actors is discussed under two sub-categories: perspective clarification and convergence to a common perspective. On the other hand, their impact on the elicitation of the intended user requirements is observed under three sub-categories: requirement elicitation, capture of the design rationale and creation of the empathy. Some qualitative and quantitative indicators are proposed to evaluate these impacts. Based on the analysis of seven observed collaborative design sessions, the findings of research study are discussed. The results points out that the major impact of these methods is that they evoke empathy for the intended users. In the groups that these methods are used the discussions are also richer regarding to the number of different needs are addressed. Moreover, these methods are also promising to keep the trace of design rationale. However design actors have tendency to accept them just as communication support, rather than documentation one. As a communication support they help design actors to clarify their arguments, to negotiate and to take decisions. However, the findings were not adequate to conclude that they have a significant impact on the perspective clarification and convergence. Hence, the main contribution of this research lies from one part in the evaluation of the impacts of these methods in requirement elicitation activity. And, in other part description of a research approach, which guides the experimental study in engineering design.