When deception becomes easy: the effects of task switching and goal neglect on the truth proportion effect.

Bram Van Bockstaele,Evelyne Debey,Christine Wilhelm,Bruno Verschuere,Ewout Meijer

doi:10.3389/fpsyg.2015.01666

Bram Van Bockstaele, Evelyne Debey + Show 3 more

Open Access

https://doi.org/10.3389/fpsyg.2015.01666

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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.

Highlights

Lying is commonly defined as “[making] an untrue statement with intent to deceive” (Lie, 2015)
In Experiment 1, we kept the number of switches on lie- and truth-trials equal to investigate whether the previously reported truth proportion effect was driven by differences in switch costs
If this were the case, we expected that the truth proportion effect would disappear, whereas we expected to replicate the truth proportion effect if it is not driven by switch costs

Summary

Introduction

Lying is commonly defined as “[making] an untrue statement with intent to deceive” (Lie, 2015). Cognitive models posit that lying requires more cognitive resources than truth telling (Gombos, 2006; Vrij et al, 2006, 2011; Blandón-Gitlin et al, 2014). These additional resources are needed—among other things—to suppress the truth, to monitor the behavior of the listener, and to fabricate and if necessary adapt the story. Recent theories propose that lying is not always more difficult than telling the truth, suggesting that the cognitive cost of lying becomes larger or smaller depending on contextual factors, and that cognitive lie detection tests should take these factors into account (e.g., see Walczyk et al, 2013)

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