The study of opinions, their formation and change, is one of the defining
topics addressed by social psychology, but in recent years other disciplines,
like computer science and complexity, have tried to deal with this issue.
Despite the flourishing of different models and theories in both fields,
several key questions still remain unanswered. The understanding of how
opinions change and the way they are affected by social influence are
challenging issues requiring a thorough analysis of opinion per se but also of
the way in which they travel between agents' minds and are modulated by these
exchanges. To account for the two-faceted nature of opinions, which are mental
entities undergoing complex social processes, we outline a preliminary model in
which a cognitive theory of opinions is put forward and it is paired with a
formal description of them and of their spreading among minds. Furthermore,
investigating social influence also implies the necessity to account for the
way in which people change their minds, as a consequence of interacting with
other people, and the need to explain the higher or lower persistence of such
changes