Trust is an important factor in negotiation and business collaboration and can be achieved through mutual understanding between characters involved in this social interaction. Only a few research using mathematical modeling treated the behavioral aspect of those characters, both rationally and emotionally. The purpose of this paper is to analyze and discuss the relationship between rational and emotional aspects of mutual understanding in a collaboration. This paper adopted and modified conventional concepts of misperception and psychological phenomena of the characters by using hypergame and attitudes analysis, respectively. First, I defined collaboration in social systems in term of normal form game-theoretical model, and then by using hypergame in which each character has their own internal model, I explained how rational understanding can be achieved. Next, using attitudes analysis, I discussed how important charactersโ attitude towards others are and showed that we need also a strong equilibrium of emotional understanding for a collaboration to produce trust as a result. Finally, this paper proposed a new concept of collaborative social systems equilibrium through such rigorous analysis.Keyword: Attitudes, Collaboration, Hypergame, Social Systems, Trust, Trustworthiness