Dynamics of Trust - Trust Theory: A Socio-Cognitive and Computational Model - page 162

6.5 The Diffusion of Trust: Authority,
Example, Contagion, Web of Trust
An interesting study about trust, partially different from the aspects so far analyzed, considers
trust diffusion in groups and networks of agents as meta-individual phenomenon , and it is
essentially based on problematics of contagion, for example, schemata, conventions, authority,
and so on. In fact, trust is sometimes a property of an environment , rather than of a single agent
or even a group: under certain conditions, the tendency to trust each other becomes diffused
in a given context, more like a sort of acquired habit or social convention than like a real
decision . These processes of 'trust spreading' are very powerful in achieving a high level of
cooperation among a large population, and should be studied in their own right.
In particular, it is crucial to understand the subtle interaction between social pressures and
individual factors in creating these 'trusting environments', and to analyze both advantages
and dangers of such diffusive forms of trust.
In our analysis, these phenomena have also to be analyzed in terms of cognitive models,
but in fact they follow slightly different rules from the ones considered in the individual
interactions, and they concern a special kind and nature of goals and tasks.
In particular, we examine the point:

how widespread trust diffuses trust ( trust atmosphere ), that is, how X 's trusting
in Y can influence Z trusting W or W' , and so on. Usually this is a macro-level
phenomenon and the individual agent does not calculate it.

Let us consider two prototypical cases, the two micro-constituents of the macro process:

i) Since X trusts Y ,also Z trusts Y
ii) Since X trusts Y , (by analogy) Z trusts W .

We would like to underline the potential multiplicative effects of those mechanisms/rules:
the process described in (i) would lead to a trust network like in Figure 6.9, while the process
described in (ii) would lead to a structure like Figure 6.10.

6.5.1 Since Z Trusts Y ,Also X Trusts Y
There are at least two mechanisms for this form of spreading of trust.

Agent's Authority (Pseudo-Transitivity)
This is the case in which, starting from the trustfulness that another agent (considered as an
authority in a specific field) expresses about a trustee, other agents decide to trust that trustee.
Consider the situation:

Bel ( XDoT ZY τ >σ 2 )( where DoT ZY τ is the degree of trust of Z on Y about the task τ )

that is:
agent X believes that Z 's degree of trust in Y on the task

τ is greater than a reasonable threshold

(following Z ).