A Fuzzy Implementation for the Socio-Cognitive Approach to Trust - Trust Theory: A Socio-Cognitive and Computational Model - page 299

11

A Fuzzy Implementation
for the Socio-Cognitive
Approach to Trust

In this chapter 1 we will show a possible implementation of the socio-cognitive model of trust
developed in the other chapters of the topic. This implementation (Falcone et al., 2005) uses
a fuzzy approach (in particular, it uses the so-called Fuzzy Cognitive Maps -FCM (Kosko,
1986). In particular our attempt is to show, using a specific implementation, how relevant a
trust model is based on beliefs and their credibility.
As previously described, our model introduced a degree of trust instead of a simple prob-
ability factor since it permits trustfulness to be evaluated in a rational way: Trust can be said
to consist of, or even better (either implicitly or explicitly) imply, the subjective probability
(in the sense of a subjective evaluation and perception of the risks and opportunities) of the
successful performance of a given behavior, and it is on the basis of this subjective percep-
tion/evaluation that the agent decides to rely or not, to bet or not on the trustee. In any case this
probability index is based on (derives from) those beliefs and evaluations. In other words, the
global, final probability of the realization of the goal g (i.e. of the successful performance of an
action ) should be decomposed into the probability of the trustee performing the action well

(that derives from the probability of its willingness, persistence, engagement, competence:
internal attributions ) and the probability of having the appropriate conditions (opportunities
and resources: external attributions ) for the performance and for its success, and of not having
interferences and adversities ( external attributions ).
In such a way we understand how the attribution of trust is a very complex task, and that
the decision making among different alternative scenarios is based on a complex evaluation
of the basic beliefs and of their own relationships. And again, how the (even minimal) change
of the credibility value of any (very relevant) belief might influence the resulting decision (and
thus the trustworthiness attributed to the trustee); or vice versa, how significant changes in the
credibility value of any unimportant belief does not significantly modify the final trust.

α

1

We would like to thank Giovanni Pezzulo for his precious contribution on this chapter.