By storing Personality Traits in User Profiles we able Recommender Systems to deduce more interesting recommendations for users acting pro-actively in order to offer for them products/services as a prediction of their future needs and behavior. This paper is proposed as an alternative to improve the robustness of recommendations by using psychological aspects, as Personality Traits. This paper is a part of a PhD ongoing work. It is presented as follow: firstly we give a brief introduction about the importance of using psychological aspects in User Profiles during the decision making process; secondly, we describe studies done in Psychology describing Personality, Traits and Tests in order to formalize how to define, to model and to extract Personality Traits of user to define his identity and to build his Profile; after, we describe how the User Reputation is formalized followed by a brief consideration about Recommender Systems; finally we present our experimentation followed by results and conclusions.