The Gullible Person: development and validation of a self-report measure of gullibility

People may have an enduring personality trait, gullibility, which makes them more likely to become scam victims. This dissertation describes the empirical development and validation of a new scale for measuring gullibility. After reviewing the relevant literature in Chapter 1, Chapter 2 reports on the development of a new, two-factor (Persuadability and Insensitivity), 12-item, Gullibility Scale. Chapter 3 presents two studies that confirm the two-factor structure of the Gullibility Scale, while also demonstrating that it is positively related to measures of paranormal beliefs and social vulnerability, negatively related to a measure of social intelligence, and not related to trust. Chapter 4 examines the scale’s test-retest reliability and criterion validity. The studies reported here showed that self-reported scam victims scored significantly higher on gullibility than did community members, psychology undergraduate students, and members of a critical thinking interest group (Skeptics). The remaining studies in this thesis examined the theoretical assertion that gullibility is a function of the ability and motivation to detect cues of untrustworthiness. Chapter 5 reports the results of two studies in which the Gullibility Scale was used to predict responses to a Prisoner’s Dilemma task that manipulated untrustworthiness cues. Although there was no relationship between scores on the Gullibility Scale and decisions made in the Prisoner’s Dilemma, the results provided confirmation that individual differences in trust and gullibility are unrelated. The final study in Chapter 6 presented participants with a series of scam emails. Gullibility was positively associated with rating scam emails as persuasive and also predicted intent to respond to them. However, there was no relationship between gullibility and cognitive ability (as measured by the Cognitive Reflection Test and Raven’s Advanced Progressive Matrices) or the ability to detect pseudo-profound bullshit. The final chapter, Chapter 7, reviews the findings of this dissertation and provides suggestions for future research.