title: When deception becomes easy: the effects of task switching and goal neglect on the truth proportion effect.
abstract: Lying is typically more cognitively demanding than truth telling. Yet, recent cognitive models of lying propose that lying can be just as easy as truth telling, depending on contextual factors. In line with this idea, research has shown that the cognitive cost of deception decreases when people frequently respond deceptively, while it increases when people rarely respond deceptively (i.e., the truth proportion effect). In the present study, we investigated two possible underlying mechanisms of the truth proportion effect. In Experiment 1 (N = 121), we controlled for the impact of switch costs by keeping the number of switches between deceptive and truthful responses constant. We found that people who often responded deceptively made fewer errors when responding deceptively than people who only occasionally responded deceptively, replicating the truth proportion effect. Thus, while the truth proportion effect in earlier studies may be partially driven by the cost of switching between truthful and deceptive responses, we still found evidence for the truth proportion effect while controlling for switch costs. In Experiment 2 (N = 68), we assessed whether the truth proportion effect is influenced by goal neglect. According to this view, the truth proportion effect should be reduced if participants are cued to maintain the task goals, while it should be larger when participants are allowed to neglect the task goals. In line with this hypothesis, we found a smaller truth proportion effect when participants were cued with the task goals compared to when they were not cued. This study shows that the truth proportion effect is influenced by goal neglect, implying that frequent deceptive responding strengthens the goal of responding deceptively. Our findings imply that the accuracy of lie detection tests could be increased by using a majority of truth-items (i.e., induce the truth proportion effect), and that the truth proportion effect should be maximized by (1) increasing the number of truth-lie task switches and (2) inducing goal neglect.
authors.affiliation: Department of Developmental Psychology, University of Amsterdam Amsterdam, Netherlands ; Department of Child Development and Education, University of Amsterdam Amsterdam, Netherlands.
authors.forename: Bram
authors.initials: B
authors.lastname: Van Bockstaele
authors.affiliation: Department of Clinical Psychology, University of Amsterdam Amsterdam, Netherlands ; Institute of Medical Psychology and Systems Neuroscience, University of Muenster Muenster, Germany.
authors.forename: Christine
authors.initials: C
authors.lastname: Wilhelm
authors.affiliation: Department of Clinical Psychological Science, Maastricht University Maastricht, Netherlands.
authors.forename: Ewout
authors.initials: E
authors.lastname: Meijer
authors.affiliation: Department of Experimental-Clinical and Health Psychology, Ghent University Ghent, Belgium.
authors.forename: Evelyne
authors.initials: E
authors.lastname: Debey
authors.affiliation: Department of Clinical Psychology, University of Amsterdam Amsterdam, Netherlands ; Department of Clinical Psychological Science, Maastricht University Maastricht, Netherlands ; Department of Experimental-Clinical and Health Psychology, Ghent University Ghent, Belgium.
authors.forename: Bruno
authors.initials: B
authors.lastname: Verschuere
keywords: deception; frequent lying; inhibition; switch cost; truth default