The Economic Reductionism and Trust (Ir)rationality - Trust Theory: A Socio-Cognitive and Computational Model - page 241

So risk perception varies very much from one subject and context to another; and the risk
can remain completely implicit in our mind.
Even trust beliefs can be implicit, not necessarily explicit and active. Not only in by default
or affect-based forms of trust (see Chapters 4 and 5), but, for example, in a routine trust
attitude, when I am used to relying on Y , and by experience I 'know' that he is reliable, and
there is nothing to worry about.
8.3 Is Trust Just the Subjective Probability of the Favorable Event?
Our main disagreement with economists is about the following issue (as we have already seen
in Section 8.1): Is trust simply reducible to subjective probability ?
This is in fact a dominant tradition in economics, game theory, part of sociology ((Gambetta,
1988); (Coleman, 1994)), and now in artificial intelligence and electronic commerce (Brainov
and Sandholm, 1999). We argue in favor of a cognitive view of trust as a complex structure of
beliefs and goals (in particular causal attributions, evaluations and expectations), even implying
that the trustor must have a 'theory of the mind' of the trustee (see Chapter 2) ((Castelfranchi
and Falcone, 1998), (Falcone and Castelfranchi, 2001)).
Such a structure of beliefs determines a 'degree of trust' and an estimation of risk, and then
a decision whether to rely on the other, which is also based on a personal threshold of risk
acceptance/avoidance (see Chapter 3).
In this chapter we use our cognitive model of trust to argue against probability reduction
and the consequent eliminative behavior. We agree with Williamson (Williamson, 1985)
that one can/should eliminate the redundant, vague, and humanistic notion of 'trust', if it
simply covers the use of subjective probability in decisions. But we strongly argue against
both this reduction and the consequent elimination. Trust cannot be reduced to a simple and
opaque index of probability because agents' decisions and behaviors depend on the specific,
qualitative evaluations and mental components. For example, internal or external attributions
of risk/success, or a differential evaluation of trustee's competence vs. willingness, make very
different predictions both about trustor's decisions and possible interventions and cautions. Let
us extensively discuss some arguments against the reduction of trust to perceived probability,
and eliminative behavior.
8.3.1 Is Trust Only about Predictability? A Very Bad Service
but a Sure One
Very frequently an economic approach - in order to reduce trust to a well known notion and
metrics (probability) - just eliminates an entire side of trust: a very typical one in common
sense, in practice, and even in economic exchanges and in labor relationships: trust as an
expectation about the quality of the good or service; trust as belief about the competence,
experience, skills of the trustee!
It seems that the only concern of trust is money, and whether to be sure or not of re-
ceiving/cumulating it. But actually even money has a quality ; not only can dollars be more
reliable than euros (or vice versa), but money can be broken, forged, out of circulation, or just
simulated!