Running head: GULLIBILITY: A REVIEW AND A SCALE Gullibility: A Review of the Literature and Devising a Self-Report Measure Alessandra Teunisse Bachelor of Psychology (Honours), Bachelor of Media (Honours) 40323862 Supervisor: Dr Trevor Case Empirical Thesis presented to the Faculty of Human Sciences Department of Psychology Macquarie University Submitted on the 8th of October, 2015, in partial fulfilment of the requirements for the degree of Master of Research Macquarie University, 2015. GULLIBILITY: A REVIEW AND A SCALE i Table of Contents Gullibility: A Review of the Literature ................................................................................... 1 Defining Gullibility .......................................................................................................... 2 Existing Research ............................................................................................................ 4 Trust and Insensitivity to Untrustworthiness Cues ........................................................ 15 Reducing Sensitivity to Untrustworthiness Cues ........................................................... 22 Motivation ...................................................................................................................... 26 Conclusion ..................................................................................................................... 28 Gullibility: Devising a Self-Report Measure ........................................................................ 30 Study 1: Exploratory Factor Analysis of Gullibility Items ............................................... 34 Method ............................................................................................................................... 34 Participants ..................................................................................................................... 34 Materials and Procedure ................................................................................................ 35 Overview of Analyses .................................................................................................... 37 Results ............................................................................................................................... 38 Data Preparation ............................................................................................................ 38 Exploratory Factor Analysis .......................................................................................... 38 Descriptive and Demographic Data ............................................................................... 41 Intercorrelations ............................................................................................................. 41 Characteristics of the Gullibility Scale .......................................................................... 42 Discussion .......................................................................................................................... 43 Study 2: Confirmatory Factor Analysis of the Gullibility Scale ....................................... 44 Method ............................................................................................................................... 44 Participants ..................................................................................................................... 44 Materials and Procedure ................................................................................................ 46 Overview of the Analyses .............................................................................................. 49 GULLIBILITY: A REVIEW AND A SCALE ii Results ............................................................................................................................... 49 Data Preparation ............................................................................................................ 49 Confirmatory Factor Analysis ....................................................................................... 49 Descriptive and Demographic Data ............................................................................... 55 Intercorrelations ............................................................................................................. 56 Discussion ......................................................................................................................... 59 General Discussion ............................................................................................................ 61 References ......................................................................................................................... 64 Appendix A: List of Online Forms .................................................................................... 82 Appendix B: Participant Information and Consent Forms ................................................ 83 Appendix C: Marlowe and Crowne Social Desirability Scale .......................................... 87 Appendix D: Gullibility Item Pool .................................................................................... 89 Appendix E: Demographic Questions for Study 1 ........................................................... 92 Appendix F: Scree Plot of Eigenvalues ............................................................................. 94 Appendix G: Gullibility Scale- Reduced ........................................................................... 95 Appendix H: Tests of Normality for the Reduced Gullibility Scale ................................. 97 Appendix I: Participant Information and Consent Forms ............................................... 100 Appendix J: Interpersonal Trust Scale ............................................................................ 104 Appendix K: Agreeableness Scale .................................................................................. 106 Appendix L: Machiavellianism Personality Scale .......................................................... 107 Appendix M: Tromsø Social Intelligence Scale .............................................................. 108 Appendix N: Demographic Questions for Study 2 ......................................................... 109 Appendix O: Standardised Regression Weights for Models ........................................... 111 Appendix P: Tests of Normality for the final Gullibility Scale and Three Factors ......... 114 Appendix Q: Ethics Approval Letters ............................................................................. 116 GULLIBILITY: A REVIEW AND A SCALE iii List of Tables Table 1. Rotated Factor Matrix .......................................................................................... 40 Table 2. Summary of Descriptive Statistics for the Gullibility and Four Factors .............. 41 Table 3. Intercorrelations Between the Variables .............................................................. 42 Table 4. Descriptive Statistics for the Variables ............................................................... 43 Table 5. Fit Indices for Various Models ............................................................................. 51 Table 6. Item Descriptions .................................................................................................. 54 Table 7. Summary of Descriptive Statistics for the Gullibility Scale Three and Factors ... 56 Table 8. Factor Correlation Matrix .................................................................................... 58 Table 9. Standardised Regression Weights for the Four Factor Model ............................. 111 Table 10. Standardised Regression Weights for the Hierarchical Model .......................... 112 GULLIBILITY: A REVIEW AND A SCALE iv List of Figures Figure 1. Model of the Gullibility Scale with the standardised regression weights ........... 54 GULLIBILITY: A REVIEW AND A SCALE v Abstract Gullibility refers to a vulnerability to being manipulated. Although almost 300,000 people in the United States of America in 2014 fell victim to various scams (Federal Bureau of Investigation Internet Crime Complaint Center, 2014), this area is surprisingly under researched. The dissertation begins with a review of the empirical literature, drawing together findings from research on the Barnum Effect, superstition, social vulnerability, scam compliance, trust, social intelligence, deception detection, and Theory of Mind. The review concludes by arguing that insensitivity to signs of untrustworthiness may be central to understanding the propensity for gullibility. Following the review, two empirical studies describe the development of a self-report measure of gullibility. In Study 1 (N = 371), a pool of items were generated and administered in an anonymous online survey. Demographic items and a measure of social desirability were also administered. An exploratory factor analysis produced a 35-item scale consisting of four factors labelled Persuadable, Trust, Unassertive, and Unsuspecting, which were not related to social desirability. In Study 2, a confirmatory factor analysis was conducted using a new sample (N = 325). Respondents completed the Gullibility Scale as well as measures of trust, agreeableness, Machiavellianism, and social intelligence. On the basis of the confirmatory factor analysis, the Trust factor was removed, which reduced the measure to a reliable 24-item scale, consisting of three factors. The Gullibility Scale had a moderate negative