Cathodal Transcranial Direct Current Stimulation on the Right Temporo-Parietal Junction Modulates the Use of Mitigating Circumstances during Moral Judgments.

Laëtitia Leloup,Yves Vandermeeren,Diana Dongo Miletich,Dana Samson,Gaëlle Andriet

doi:10.3389/fnhum.2016.00355

Laëtitia Leloup, Yves Vandermeeren + Show 3 more

Open Access

https://doi.org/10.3389/fnhum.2016.00355

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Abstract

Recently, a few transcranial magnetic stimulation or transcranial direct current stimulation (tDCS) studies have shown that the right temporo-parietal junction (rTPJ) plays a causal role in moral reasoning especially in cases of accidental harms or attempted harms. The profile of results across studies is, however, not entirely consistent: sometimes the stimulation affects predominantly attempted harms while sometimes the stimulation affects predominantly accidental harms. We argue that such discrepancy could reflect different functional contributions of the rTPJ in moral judgments and that the chosen design parameters or stimulation method may differentially bring to light one or the other functional role of the rTPJ. In the current study, we found that tDCS specifically affected accidental harms but not attempted harms. Low cathodal stimulation of the rTPJ led to a marginally significant increase in the severity of judgments of accidental harms (Experiment 1) while higher cathodal current density led to a highly significant decrease in the severity of judgments of accidental harms (Experiment 2). Our pattern of results in the context of our experimental design can best be explained by a causal role of the rTPJ in processing the mitigating circumstances which reduce a protagonist’s moral responsibility. We discuss these results in relation to the idea that the rTPJ may play multiple roles in moral cognition and in relation to methodological aspects related to the use of tDCS.

Highlights

IntroductionThe right temporo-parietal junction (rTPJ) is seen as one of the key regions of what is commonly coined the “theory of mind network” (Saxe and Kanwisher, 2003; Young et al, 2010b; Krall et al, 2014; Schurz et al, 2014), i.e., the brain network sustaining our ability to explain and predict someone’s behavior on the basis of his or her mental states (Premack and Woodruff, 1978).rTPJ Stimulation and Moral JudgmentsMore recently, the rTPJ has been associated with moral reasoning, i.e., when participants are asked what someone ought to do (Greene et al, 2001; Koenigs et al, 2007) or when participants are asked to judge whether what someone is doing is permissible, should be blamed or should be punished (Young et al, 2007; Cushman, 2008; Young and Saxe, 2008; Koster-Hale et al, 2013; Yoder and Decety, 2014).The majority of the studies which have shown the involvement of the rTPJ in moral cognition are imaging studies which only provide correlational evidence
The results of Experiment 1 showed a marginal effect (1) of cathodal stimulation only and (2) on accidental harm scenarios only. This pattern of result is in line with the idea that the right temporo-parietal junction (rTPJ) may play a role in the consideration of mitigating circumstances when attributing moral responsibility
We found that cathodal transcranial direct current stimulation (tDCS) applied to the rTPJ modulated the moral judgments of accidental harms; judgments of attempted harms were not affected

Summary

Introduction

The right temporo-parietal junction (rTPJ) is seen as one of the key regions of what is commonly coined the “theory of mind network” (Saxe and Kanwisher, 2003; Young et al, 2010b; Krall et al, 2014; Schurz et al, 2014), i.e., the brain network sustaining our ability to explain and predict someone’s behavior on the basis of his or her mental states (Premack and Woodruff, 1978).rTPJ Stimulation and Moral JudgmentsMore recently, the rTPJ has been associated with moral reasoning, i.e., when participants are asked what someone ought to do (Greene et al, 2001; Koenigs et al, 2007) or when participants are asked to judge whether what someone is doing is permissible, should be blamed or should be punished (Young et al, 2007; Cushman, 2008; Young and Saxe, 2008; Koster-Hale et al, 2013; Yoder and Decety, 2014).The majority of the studies which have shown the involvement of the rTPJ in moral cognition are imaging studies which only provide correlational evidence. It has been extensively documented in the theory of mind literature that the rTPJ is sensitive to situations where an agent holds a false belief (e.g., Saxe and Kanwisher, 2003; Perner et al, 2006), that is, when there is a mismatch between the agent’s perspective (what the agent falsely thinks about the state of the world) and the participant’s perspective (what the participant knows is the true state of the world) According to this interpretation of the role of the rTPJ, one would expect the rTPJ stimulation to only affect moral judgments in the attempted harm and accidental harm scenarios. The reverse reasoning is applied to the inhibitory stimulation which would be more likely to decrease the contribution of belief representations in the attempted harm scenarios (where the rTPJ is more activated because of the harmful intention) than in the accidental harm scenarios (where the rTPJ is less activated because of the neutral intention)

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