Trust dynamics: how trust is influenced by direct experiences and by trust itself

In this paper we will examine two main aspects of trust dynamics: a) How direct experiences involving trust, with their successes or failures, influence the future trust of an agent about similar facts. We challenge the trivial idea that always success increases trust while failure decreases it. Of course, this primitive view cannot be avoided till Trust is modeled just as a simple index, a dimension, a number; for example reduced to mere subjective probability. We claim that a cognitive attribution process is needed in order to update trust on the basis of an 'interpretation' of the outcome of A's reliance on B and of B's performance (failure or success). b) How the fact that A trusts B and relies on it in situation Ω can actually (objectively) influence B's trustworthiness in the /Spl Omega/ situation. Either trust is a selffulfilling prophecy that modifies the subjective probability of the predicted event; or it is a self-defeating strategy by negatively influencing the events. These phenomena are very crucial in human societies (states, market, groups), but also in computer mediated Organizations, Interactions (EC), Cooperation (CSCW) and even in Multi-Agent Systems with autonomous agents. We present a formal model of these dynamic nontrivial aspects.