On Trust

On Trust
Massimo Felici

Massimo Felici On Trust c 2008-2012

1

Outline
• What is Trust?

• Trust matters

• Trust problems

• Seeking an Experimental Trust Framework

• Trust and Dependability

• Directions for future work


What is Trust? 2

Constructive Trust
Diﬀerent Trust Features or Meanings

• Diﬀerent meanings of trust

• Characterization of trust in terms of basic constructs: Trusting Intention,
Trusting Behavior, Trusting Beliefs, System Trust, Dispositional Trust and
Situational Decision to Trust

• Trust features, e.g.: Competence, Predictability, Benevolence and Integrity

References: [5, 6, 7, 8]


What is Trust? 3

Relational Trust
• Trust is relational
• Trust as a three-part relation
A Trusts B in to do X or in matters Y
• Trust depends on the context or situation
• Trust is subjective: “trust (or, symmetrically, distrust) is a particular level of
the subjective probability with which an agent assesses that another agent or
group of agents will perform a particular action, both before he can monitor
such action (or independently of his capacity ever to be able to monitor it)
and in a context in which it aﬀects his own action.”
References: [2]


What is Trust? 4

Trustworthiness
• “In general, the complexity of the problem of trust derives primarily from the
complexity of the problem of trustworthiness. [...] the motivations for being
trustworthy are manifold. In a sense, trusting someone in some context is
simply to be explained as merely the expectation that the person will most
likely be trustworthy.”

• Inducements: internal (e.g., moral rules, interests, consequences, etc.),
external (e.g., social constraints, institutional constraints, norms, etc.) or
mixed.

References: [3]


What is Trust? 5

Rational Trust
• Rational theory of trust... Trust as a rational choice

• Encapsulated-interest model of Trust
“Your trust turns not directly on your own interests but rather on whether
these are encapsulated in the interests of the trusted. You trust someone if
you believe it will be in her interest to be trustworthy in the relevant way
at the relevant time, and it will be in her interest because she wishes to
maintain her relationship with you.”

References: [3]


What is Trust? 6

Distrust
• dual concept of trust

• like Trust, a three-part relationship
A distrust B with respect to X

• like Trust, a matter of degree

• asymmetries between Trust and Distrust: asymmetric grounds (motivational
and epistemological), asymmetric societal implications


Trust Matters 7

Interactions
• One-way Trust (iterated)

• Mutual Trust (e.g., Prisoner’s Dilemma)
• Thick Relationships (e.g., social and institution relationships, group
memberships, etc.)


Trust Matters 8

Interactions
• Increasing complexity of interaction

• Diﬀerent mechanisms work/cope with diﬀerent complexities

• Local trust relationships do not scale up


Trust Matters 9

Considerations on Interactions
• Thick relationships expose the limitations of games — games poorly capture
knowledge about thick relationships

• games capture cooperative interactions, rather than trust

• games need to be interpreted with respect to contextual relationships – local
relationships might be easy to capture/model/understand/formalise/...; on
the other hand, some global phenomena may be little inﬂuenced by thick
relationships

• Local and Global Trust


Trust Matters 10

Structures
• there is yet little understanding how emerging socio-technical structures (e.g.,
organizations, responsibilities, etc.) aﬀect trust

• Other structural dependencies: Dependability, Risk perception

• Structure Complexity

• Diverse Structures: Formal structures, Social structures (e.g., Social Networks),
Institutional structures (e.g., Responsibilities)

Is there any implication from the social theory of risk?
References: [1]


Trust Matters 11

A Formal Trust Structure
• A trust structure T is a triple T = (D, , ), where and are binary
orderings on a set of values D.

• t s means that s represents a higher degree of trust than t

• information ordering or reﬁnement:

References: [4]


Trust Matters 12

Knowledge Uncertainty and Risk
• Trust involves knowledge uncertainty, hence, risk — “to acto on trust is to
take a risk, although trust is not itself a matter of deliberately taking a risk
because it is not a matter of making a choice.”
References: [3]
• This is, however, a simplistic interpretation of the relationships among trust,
knowledge uncertainty and risk
• The better our understanding, the better the trust mechanisms that mitigate
risk in presence of knowledge uncertainty

Is there any implication for Risk Theory? Risky systems involve complex
interactions, hence, do they require trust?
References: [9]


Trust Problems 13

Modelling Interaction
• Games are a natural means for modelling interaction

• Three-part relation: A Trusts B in to do X or in matters Y

• Encapsulated-interest model of Trust

• Local and Global Interaction

• How to capture thick relationships (e.g., complex emerging
relationships)?


Trust Problems 14

Quantifying Trust
• Measuring Trust

• Probabilistic view of trust (e.g., bayesian models of Trust)

• Events affect trust estimation
“An event structure is a triple ES = (E, ≤, ) consisting of a set E of events
which are partially ordered by ≤, the necessity (or casuality) relation; the
conflict relation is a binary, symmetric, irreflexive relation on events.”


15

Seeking an Experimental Trust Framework
• Trust Relation and Interaction: A trusts B to do X, in matters Y or to
discharge responsibility Z

• Encapsulated-trust model: encapsulating inducements

• Event Structures: ES = (E, ≤, ), ordering on events; causality relationship

• Trust Structures: T = (D, , ); ordering degrees of trust; reﬁnement on
information

• Thick Relationships (e.g., social relationships, group memberships, etc.)


16

Seeking an Experimental Trust Framework
• Trust Relation and Interaction: A trusts B to do X, in matters Y or to
discharge responsibility Z

• Encapsulated-trust model: encapsulating inducements

• Trust Structures: ordering degrees of trust; reﬁnement on information

• Trust Events: ordering on events; causality relationship

• Trust Information

• Thick Relationships (e.g., social relationships, group memberships, etc.)


Dependability Aspects 17

Trust and Confidence
• Experts estimate their confidence (i.e., “the probability that a claim is true”)
on different claims

• The combinations of different arguments present some uncertainty and
contingency – for instance, despite the emergence of further knowledge
strengthening one of the claims, the overall confidence on the claim could
decrease

• Is it possible to analyse the (multi-leg argument) confidence problem as an
interaction/game problem?

• Is it possible to interpret the confidence problem with respect to trust? This
would tell us how trust/confidence differ.



Trust and Responsibilities
• How does Trust extend Responsibility models?

• Relational Trust: A trusts B to discharge responsibility X

• Trust models involve many tree-part relationships over responsibilities

• How to extend emerging structures by thick relationships (e.g., social
or institutional relationships)?



Trust and Timing
• Event structures order and constrain occurring events

• Time bands define different focuses

• Trust might emerge over different time bands


20

Other Trust Aspects
• Trust as process

• Trust as routine – taken-for-granted

• Trust in Multi-Agent Systems

• Trust and Performance

• Organizational Trust

• Deciding when Trust is enough


21

Summary
• Overview of Trust aspects and concepts (e.g., Distrust, Trustworthiness, etc.)

• Basic models: relational (e.g., three-part relation, thick relationships),
encapsulated-interest model, interaction (games), trust structures and
probabilistic trust (depending on events).

• How do the basic models relate to each other? Integrating them?

• Can we use/tailor them for structuring empirical analyses on Trust?


22

Directions for Future Work
• Analysing/Modelling Trust in diﬀerent application domains

• Developing Examples of Trust Problems

• Seeking an Experimental Approach to Trust: Requirements

• Developing an Experimental Approach to Trust: Modelling Framework,
Experimental Analysis

• Looking at diﬀerent Case Studies and Empirical investigations


23

References
[1] Mary Douglas and Aaron Wildavsky. Risk and Culture: An Essay on the Selection of Technological and Environmental Dangers.
University of California Press, 1982.
[2] Diego Gambetta, editor. Trust: Making and Breaking Cooperative Relations. Basil Blackwell, 1998.
[3] Russell Hardin, editor. Trust and Trustworthiness. Russell Sage Foundation, 2002.
[4] Karl Krukow and Mogens Nielsen. Trust structures: Denotational and operational semantics. International Journal of Information
Security, 6(2-3):153–181, 2007.
[5] D. Harrison McKnight and Norman L. Chervany. The meanings of trust. Technical Report 96-04, University of Minnesota, Management
Informations Systems Research Center (MISRC), 1996.
[6] D. Harrison McKnight and Norman L. Chervany. What is trust? a conceptual analysis and an interdisciplinary model. In Proceedings
of the Americas Conference on Information Systems, pages 827–833, 2000.
[7] D. Harrison McKnight and Norman L. Chervany. Conceptualizing trust: A typology and e-commerce customer relationships model. In
Proceedings of the 34th Hawaii Conference on System Sciences (HICSS-34), volume 7, page 7022. IEEE Computer Society, 2001.
[8] D. Harrison McKnight and Norman L. Chervany. Trust and distrust deﬁnitions: One bite at a time. In R. Falcone, M. Singh, and Y.-H.
Tan, editors, Proceedings of Trust in Cyber-societies, number 2246 in LNAI, pages 27–54. Springer-Verlag, 2001.
[9] Charles Perrow. Normal Accidents: Living with High-Risk Technologies. Princeton University Press, 1999.


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