Trust Theory

Cristiano Castelfranchi is full professor of Cognitive Sciences at the University of Siena, Italy, and Director of the Institute of the Cognitive Sciences and Technologies (ISTC) of the Italian National Research Council (CNR). Cristiano has a background in linguistics and psychology, and is active in the Multi-Agent Systems, Social Simulation, and Cognitive Science communities. He was program chair of AAMAS 2002, and is chair of several international workshops. He has published 11 books (3 in English), and more than 150 conference and journal articles. Rino Falcone is Leader Researcher for the T3 (Trust Theory and Technology) group at the Institute of the Cognitive Sciences and Technologies (ISTC) of the Italian National Research Council (CNR). His scientific interests include Natural Language Processing, Plan Recognition, Multi-agent Systems and Agent Theory.  Rino has published more than 100 conference and journal articles, organized several international conferences, and edited several special issues of international journal on these topics.

Foreword xv

Introduction 1

1 Definitions of Trust: From Conceptual Components to the General Core 7

1.1 A Content Analysis 8

1.2 Missed Components and Obscure Links 12

1.3 Intentional Action and Lack of Controllability: Relying on What is Beyond Our Power 15

1.4 Two Intertwined Notions of Trust: Trust as Attitude vs. Trust as Act 17

1.5 A Critique of Some Significant Definitions of Trust 19

1.5.1 Gambetta: Is Trust Only About Predictability? 19

1.5.2 Mayer, Davis, & Schoorman: Is Trust Only Willingness, for Any Kind of Vulnerability? 19

1.5.3 McKnight: The Black Boxes of Trust 21

1.5.4 Marsh: Is a Mere Expectation Enough for Modeling Trust? 21

1.5.5 Yamagishi: Mixing up the Act of Trusting and the Act of Cooperating 22

1.5.6 Trust as Based on Reciprocity 26

1.5.7 Hardin: Trust as Encapsulated Interest 26

1.5.8 Rousseau: What Kind of Intention is ‘Trust’? 30

References 31

2 Socio-Cognitive Model of Trust: Basic Ingredients 35

2.1 A Five-Part Relation and a Layered Model 36

2.1.1 A Layered Notion 36

2.1.2 Goal State and Side Effects 38

2.2 Trust as Mental Attitude: a Belief-Based and Goal-Based Model 38

2.2.1 Trust as Positive Evaluation 39

2.2.2 The ‘Motivational’ Side of Trust 44

2.2.3 The Crucial Notion of ‘Goal’ 45

2.2.4 Trust Versus Trustworthiness 47

2.2.5 Two Main Components: Competence Versus Predictability 47

2.2.6 Trustworthiness (and trust) as Multidimensional Evaluative Profiles 49

2.2.7 The Inherently Attributional Nature of Trust 50

2.2.8 Trust, Positive Evaluation and Positive Expectation 52

2.3 Expectations: Their Nature and Cognitive Anatomy 54

2.3.1 Epistemic Goals and Activity 54

2.3.2 Content Goals 55

2.3.3 The Quantitative Aspects of Mental Attitudes 56

2.3.4 The Implicit Counterpart of Expectations 58

2.3.5 Emotional Response to Expectation is Specific: the Strength of Disappointment 58

2.3.6 Trust is not Reducible to a Positive Expectation 60

2.4 ‘No Danger’: Negative or Passive or Defensive Trust 60

2.5 Weakening the Belief-Base: Implicit Beliefs, Acceptances, and Trust by-Default 62

2.6 From Disposition to Action 64

2.6.1 Trust That and Trust in 66

2.6.2 Trust Pre-disposition and Disposition: From Potential to Actual Trust 67

2.6.3 The Decision and Act of Trust Implies the Decision to Rely on 69

2.7 Can we Decide to Trust? 72

2.8 Risk, Investment and Bet 73

2.8.1 ‘Risk’ Definition and Ontology 74

2.8.2 What Kinds of Taken Risks Characterize Trust Decisions? 76

2.9 Trust and Delegation 77

2.9.1 Trust in Different Forms of Delegation 79

2.9.2 Trust in Open Delegation Versus Trust in Closed Delegation 80

2.10 The Other Parts of the Relation: the Delegated Task and the Context 82

2.10.1 Why Does X Trust Y? 82

2.10.2 The Role of the Context/Environment in Trust 83

2.11 Genuine Social Trust: Trust and Adoption 84

2.11.1 Concern 88

2.11.2 How Expectations Generate (Entitled) Prescriptions: Towards ‘Betrayal’ 88

2.11.3 Super-Trust or Tutorial Trust 89

2.12 Resuming the Model 91

References 92

3 Socio-Cognitive Model of Trust: Quantitative Aspects 95

3.1 Degrees of Trust: a Principled Quantification of Trust 95

3.2 Relationships between Trust in Beliefs and Trust in Action and Delegation 97

3.3 A Belief-Based Degree of Trust 98

3.4 To Trust or Not to Trust: Degrees of Trust and Decision to Trust 101

3.5 Positive Trust is not Enough: a Variable Threshold for Risk Acceptance/Avoidance 107

3.6 Generalizing the Trust Decision to a Set of Agents 111

3.7 When Trust is Too Few or Too Much 112

3.7.1 Rational Trust 112

3.7.2 Over-Confidence and Over-Diffidence 112

3.8 Conclusions 114

References 115

4 The Negative Side: Lack of Trust, Implicit Trust, Mistrust, Doubts and Diffidence 117

4.1 From Lack of Trust to Diffidence: Not Simply a Matter of Degree 117

4.1.1 Mistrust as a Negative Evaluation 118

4.2 Lack of Trust 119

4.3 The Complete Picture 120

4.4 In Sum 121

4.5 Trust and Fear 122

4.6 Implicit and by Default Forms of Trust 122

4.6.1 Social by-Default Trust 124

4.7 Insufficient Trust 125

4.8 Trust on Credit: The Game of Ignorance 126

4.8.1 Control and Uncertainty 126

4.8.2 Conditional Trust 127

4.8.3 To Give or Not to Give Credit 127

4.8.4 Distrust as Not Giving Credit 129

References 131

5 The Affective and Intuitive Forms of Trust: The Confidence We Inspire 133

5.1 Two Forms of ‘Evaluation’ 134

5.2 The Dual Nature of Valence: Cognitive Evaluations Versus Intuitive Appraisal 134

5.3 Evaluations 135

5.3.1 Evaluations and Emotions 136

5.4 Appraisal 137

5.5 Relationships Between Appraisal and Evaluation 138

5.6 Trust as Feeling 140

5.7 Trust Disposition as an Emotion and Trust Action as an Impulse 141

5.8 Basing Trust on the Emotions of the Other 142

5.9 The Possible Affective Base of ‘Generalized Trust’ and ‘Trust Atmosphere’ 143

5.10 Layers and Paths 143

5.11 Conclusions About Trust and Emotions 144

References 145

6 Dynamics of Trust 147

6.1 Mental Ingredients in Trust Dynamics 148

6.2 Experience as an Interpretation Process: Causal Attribution for Trust 150

6.3 Changing the Trustee’s Trustworthiness 154

6.3.1 The Case of Weak Delegation 154

6.3.2 The Case of Strong Delegation 158

6.3.3 Anticipated Effects: A Planned Dynamics 161

6.4 The Dynamics of Reciprocal Trust and Distrust 164

6.5 The Diffusion of Trust: Authority, Example, Contagion, Web of Trust 168

6.5.1 Since Z Trusts Y, Also X Trusts Y 168

6.5.2 Since X Trusts Y, (by Analogy) Z Trusts W 173

6.5.3 Calculated Influence 173

6.6 Trust Through Transfer and Generalization 174

6.6.1 Classes of Tasks and Classes of Agents 175

6.6.2 Matching Agents’ Features and Tasks’ Properties 175

6.6.3 Formal Analysis 177

6.6.4 Generalizing to Different Tasks and Agents 178

6.6.5 Classes of Agents and Tasks 182

6.7 The Relativity of Trust: Reasons for Trust Crisis 184

6.8 Concluding Remarks 188

References 189

7 Trust, Control and Autonomy: A Dialectic Relationship 191

7.1 Trust and Control: A Complex Relationship 191

7.1.1 To Trust or to Control? Two Opposite Notions 192

7.1.2 What Control is 192

7.1.3 Control Replaces Trust and Trust Makes Control Superflous? 195

7.1.4 Trust Notions: Strict (Antagonist of Control) and Broad (Including Control) 196

7.1.5 Relying on Control and Bonds Requires Additional Trust: Three Party Trust 198

7.1.6 How Control Increases and Complements Trust 200

7.1.7 Two Kinds of Control 201

7.1.8 Filling the Gap between Doing/Action and Achieving/Results 203

7.1.9 The Dynamics 204

7.1.10 Control Kills Trust 205

7.1.11 Resuming the Relationships between Trust and Control 206

7.2 Adjusting Autonomy and Delegation on the Basis of Trust in Y 206

7.2.1 The Notion of Autonomy in Collaboration 209

7.2.2 Delegation/Adoption Theory 209

7.2.3 The Adjustment of Delegation/Adoption 213

7.2.4 Channels for the Bilateral Adjustments 222

7.2.5 Protocols for Control Adjustments 223

7.2.6 From Delegation Adjustment to Autonomy Adjustment 225

7.2.7 Adjusting Meta-Autonomy and Realization-Autonomy of the Trustee 225

7.2.8 Adjusting Autonomy by Modyfing Control 226

7.2.9 When to Adjust the Autonomy of the Agents 227

7.3 Conclusions 230

References 232

8 The Economic Reductionism and Trust (Ir)rationality 235

8.1 Irrational Basis for Trust? 236

8.1.1 Is Trust a Belief in the Other’s Irrationality? 236

8.2 Is Trust an ‘Optimistic’ and Irrational Attitude and Decision? 239

8.2.1 The Rose-Tinted Glasses of Trust 239

8.2.2 Risk Perception 246

8.3 Is Trust Just the Subjective Probability of the Favorable Event? 247

8.3.1 Is Trust Only about Predictability? A Very Bad Service but a Sure One 247

8.3.2 Probability Collapses Trust ‘that’ and ‘in’ 248

8.3.3 Probability Collapses Internal and External (Attributions of) Trust 248

8.3.4 Probability Misses the Active View of Trust 250

8.3.5 Probability or Plausibility? 250

8.3.6 Probability Reduction Exposes to Eliminative Behavior: Against Williamson 250

8.3.7 Probability Mixes up Various Kinds of Beliefs, Evaluations, Expectations about the Trustee and Their Mind 252

8.4 Trust in Game Theory: from Opportunism to Reciprocity 254

8.4.1 Limiting Trust to the Danger of Opportunistic Behavior 255

8.4.2 ‘To Trust’ is not ‘to Cooperate’ 255

8.5 Trust Game: A Procuste’s Bed for Trust Theory 256

8.6 Does Trust Presuppose Reciprocity? 258

8.7 The Varieties of Trust Responsiveness 260

8.8 Trusting as Signaling 260

8.9 Concluding Remarks 261

References 261

9 The Glue of Society 265

9.1 Why Trust is the ‘Glue of Society’ 265

9.2 Trust and Social Order 266

9.2.1 Trust Routinization 268

9.3 How the Action of Trust Acquires the Social Function of Creating Trust 268

9.4 From Micro to Macro: a Web of Trust 270

9.4.1 Local Repercussions 270

9.4.2 Trans-Local Repercussions 271

9.5 Trust and Contracts 272

9.5.1 Do Contracts Replace Trust? 272

9.5.2 Increasing Trust: from Intentions to Contracts 272

9.5.3 Negotiation and Pacts: Trust as Premise and Consequence 275

9.6 Is Trust Based on Norms? 275

9.6.1 Does Trust Create Trust and does There Exist a Norm of Reciprocating Trust? 277

9.7 Trust: The Catalyst of Institutions 278

9.7.1 The Radical Trust Crisis: Institutional Deconstruction 279

References 279

10 On the Trustee’s Side: Trust As Relational Capital 281

10.1 Trust and Relational Capital 282

10.2 Cognitive Model of Being Trusted 284

10.2.1 Objective and Subjective Dependence 285

10.2.2 Dependence and Negotiation Power 289

10.2.3 Trust Role in Dependence Networks 292

10.3 Dynamics of Relational Capital 297

10.3.1 Increasing, Decreasing and Transferring 297

10.3.2 Strategic Behavior of the Trustee 300

10.4 From Trust Relational Capital to Reputational Capital 301

10.5 Conclusions 302

References 302

11 A Fuzzy Implementation for the Socio-Cognitive Approach to Trust 305

11.1 Using a Fuzzy Approach 306

11.2 Scenarios 306

11.3 Belief Sources 307

11.4 Building Belief Sources 307

11.4.1 A Note on Self-Trust 309

11.5 Implementation with Nested FCMs 310

11.6 Converging and Diverging Belief Sources 311

11.7 Homogeneous and Heterogeneous Sources 312

11.8 Modeling Beliefs and Sources 312

11.9 Overview of the Implementation 313

11.9.1 A Note on Fuzzy Values 315

11.10 Description of the Model 316

11.11 Running the Model 316

11.12 Experimental Setting 317

11.12.1 Routine Visit Scenario 317

11.12.2 Emergency Visit Scenario 319

11.12.3 Trustfulness and Decision 320

11.12.4 Experimental Discussion 321

11.12.5 Evaluating the Behavior of the FCMs 322

11.12.6 Personality Factors 322

11.13 Learning Mechanisms 323

11.13.1 Implicit Revision 324

11.13.2 Explicit Revision 324

11.13.3 A Taxonomy of Possible Revisions 325

11.14 Contract Nets for Evaluating Agent Trustworthiness 326

11.14.1 Experimental Setting 326

11.14.2 Delegation Strategies 327

11.14.3 The Contract Net Structure 328

11.14.4 Performing a Task 329

11.14.5 FCMs for Trust 329

11.14.6 Experiments Description 330

11.14.7 Using Partial Knowledge: the Strength of a Cognitive Analysis 333

11.14.8 Results Discussion 339

11.14.9 Comparison with Other Existing Models and Conclusions 341

References 342

12 Trust and Technology 343

12.1 Main Difference Between Security and Trust 344

12.2 Trust Models and Technology 345

12.2.1 Logical Approaches 346

12.2.2 Computational Approach 347

12.2.3 Different Kinds of Sources 347

12.2.4 Centralized Reputation Mechanisms 348

12.2.5 Decentralized Reputation Mechanisms 349

12.2.6 Different Kinds of Metrics 350

12.2.7 Other Models and Approaches to Trust in the Computational Framework 351

12.3 Concluding Remarks 354

References 354

13 Concluding Remarks and Pointers 359

13.1 Against Reductionism 359

13.2 Neuro-Trust and the Need for a Theoretical Model 360

13.3 Trust, Institutions, Politics (Some Pills of Reflection) 361

13.3.1 For Italy (All’Italia) 362

References 363

Index 365