Within-subjects verbal lie detection measures: a comparison between total detail and proportion of complications

Background: We examined whether the verbal cue, proportion of complications, was a more diagnostic cue to deceit than the amount of information provided (e.g., total number of details).

Method: In the experiment, 53 participants were interviewed. Truth tellers (n = 27) discussed a trip they had made during the last twelve months; liars (n = 26) fabricated a story about such a trip. The interview consisted of an initial recall followed by a model statement (a detailed account of an experience unrelated to the topic of investigation) followed by a post-model statement recall. The key dependent variables were the amount of information provided and the proportion of all statements that were complications.

Results: The proportion of complications was significantly higher amongst truth tellers than amongst liars, but only in the post-model statement recall. The amount of information provided did not discriminate truth tellers from liars in either the initial or post-model statement recall.

Conclusion: The proportion of complications is a more diagnostic cue to deceit than the amount of information provided as it takes the differential verbal strategies of truth tellers and liars into account.