Further Insights into Truth-Default Theory
: A Deception Detection Experiment

  • Daniel Malmgren

Student thesis: Master, one year


People seem to rarely consider whether a communicated narrative is deceptive. The aim of this study was to replicate previous findings about the truth-default theory, and to provide further insights into the effects of the truth-default state in processing another’s communication. The Truth-Default theory provides a framework for understanding people’s tendency to operate on a presumption of honesty. The experiment reported in this study used video-recorded narratives and four betweensubject factors in investigating the effects of different types of triggers on the truth-default state. A total of six hypotheses were studied: hypothesis one through three were about replicating previous findings on the occurrence and frequency of thoughts pertaining to veracity or deception, the levels of truth-bias, deception detection accuracy and the importance of plausibility in comparison to actual veracity. Hypothesis four through six predicted effects of semantic priming, implausible message content and possible mediating effects on ratings of credibility and reliance through liar representativity and plausibility. In summary, prior findings on the truth-default state replicated and were corroborated. The outcome of the experiment done by 106 participants online indicates that people tend to passively assume that others are honest and that communicated narratives are reliable. The result calls for renewed attention to the risks of malign information influence posed by junk news producers and others. It also highlights the importance of educating in and developing source criticism skills.
Date of Award2022-Jun
Original languageEnglish
SupervisorMarcus Johansson (Supervisor) & Peter Jönsson (Examiner)

Courses and Subjects

  • Psychology

University credits

  • 15 HE credits

Swedish Standard Keywords

  • Psychology (50101)


  • Lying
  • deception
  • bias
  • tendency
  • truth-default theory
  • source criticism

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