“Do not trust people - they are capable of greatness”

Stanislaw Lem

Trust ModelsSteve Marsh

Carleton University, November 2nd 2009steve.marsh@crc.gc.ca

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Outline

Why

What

How

Why…

Trust as Syllogism

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Yes, but why in agents?

Societies and decisions

What…

… is it?

No wait!

What…

… isn’t it?

What…

… is it?

Trust is complexity reduction

Trust is history

Trust is reasoning

Trust is observability

Trust is not control

Trust is risk in action

Trust is seen in action

Or the air

Like light

Don’t just talk about it, do it…And see it…

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Caveat…

What… On Trust Models

Types

Functions

Representations

Models of Trust

Cognitive

Game-Theoretical

Hybrid (possibly)

Modes

(so, what’s it for?How’s it work?)

Establishment

Establishment

Reasoning

Establishment

Reasoning

Action

Representations

Fuzzy Terms

Logic

Real Numbers

Integers

Vectors

How…Two ‘real life’ models

Marsh; 1994, 2009Castelfranchi (et al); (various), 2009

(there are lots more…)

Types of Trust

The Marsh Model

Types of Trust 1:Basic

€

Tx

The Marsh Model

Types of Trust 2:General

€

Tx (y)

The Marsh Model

Types of Trust 3:Situational

€

Tx (y,α )

The Marsh Model

How much do I have?

€

Tx (y,α ) = Ux (α ) × Ix (α ) ×) T x (y)

The Marsh Model

How much do I need?

€

C _ Tx (y) =Riskx (α )

Competencex (y,α ) +) T x (y)

× Ix (α )

The Marsh Model

Do I ‘Trust’ Thee?

€

Tx (y,α ) ≥ C _ Tx(y,α ) → Trustsx (y,α )

The Marsh Model

Distrust, Mistrust, Untrust, Ambivalence

Oh My!

The Marsh Model

Regret

€

Regret x (α ) = (Ux (α ) −Ux (α −)) • f (κ ,λ ,μ)

The Marsh Model

Regret Adapts Trust (with Understanding)

€

f =C _ Tx (α )t + Tx (y,α )t

Ξx

× (Regret x (α ) − Regret y (α ))

The Marsh Model

Anticipatory Regret

€

C _Tx (y) =Riskx (α )

Competencex (y,α ) +) T x (y)

× (Ix (α ) − ARx (α −))

The Marsh Model

Forgiveness Repairs Trust

€

Tx (y)t +tFtx = Tx (y)t +tFtx−1 + Fkx

The Marsh Model

Forgiveness Function

€

Fkx =(Regret y (α ) − Regret x (α ) + Ix (xy))

Ftx

× Tx (y)

(There are limits to Forgiveness)The Marsh Model

Continuum

-1 10Distrust Trust

UntrustC_TLimit of

Forgivability

The Marsh Model

A Logical Model

The Castelfranchi et al. Model

Core Trust and(Generalized) core trust

The Castelfranchi et al. Model

€

CoreTrust (i, j,α ,ϕ ) = GoaliXϕ ∧Plausi(Afterj:αϕ ∧Int j (α )∧I Pre( j,α )∧E Pre( j,α ))

Distrust and(Generalized) distrust

The Castelfranchi et al. Model

€

Distrust(i, j,α ,ϕ ) = Goali Xϕ ∧Plausi(¬ Afterj:αϕ ∨¬ Int j (α )∨¬ I Pr e( j,α )∨¬ E Pr e( j,α ))

Mistrust and(Generalized) mistrust

The Castelfranchi et al. Model

€

Mistrust(i, j,α ,ϕ ) = Goali Xϕ ∧Plausi (Afterj:α¬ ϕ ∧Int j (α )∧I Pr e( j,α )∧E Pr e( j,α ))

Delegation (reliance)

The Castelfranchi et al. Model

€

Delegate(i, j,α ,ϕ ) = GoaliDoes j:αϕ

Decision to trust

The Castelfranchi et al. Model

€

DecideTrust (i, j,α ,ϕ ) = CoreTrust (i, j,α ,ϕ )∧Delegate(i, j,α ,ϕ )

Comparative Trust

The Castelfranchi et al. Model

€

(z,β,ϕ ) <iTrust ( j,α ,ϕ ) =

Goali Xϕ ∧

((Afterz:βϕ ∧Intzβ∧I Pr e(z,β )∧E Pr e(z,β )) <i

((Afterj:αϕ ∧Int jα ∧I Pr e( j,α )∧E Pr e( j,α ))

Expressiveness and non-reductionismvs

Implementability

Where does it all fit?

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Where to look for information

Start here… And here…

Try a google search…

“Never trust a man who, when left alone in a room with a tea

cosy, doesn’t try it on”

Billy Connelly