Brief articlePushing moral buttons: The interaction between personal force and intention in moral judgment
Introduction
Many moral and political controversies involve a tension between individual rights and the greater good (Singer, 1979). This tension is nicely captured by a puzzle known as the “trolley problem” that has long interested philosophers (Foot, 1978, Thomson, 1985) and that has recently become a topic of sustained neuroscientific (Ciaramelli et al., 2007, Greene et al., 2004, Greene et al., 2001, Koenigs et al., 2007, Mendez et al., 2005, Schaich Borg et al., 2006) and psychological (Cushman et al., 2006, Greene et al., 2008, Hauser et al., 2007, Mikhail, 2000, Mikhail, 2007, Moore et al., 2008, Nichols and Mallon, 2005, Waldmann and Dieterich, 2007) investigation. One version of the trolley problem is as follows: A runaway trolley is about to run over and kill five people. In the switch dilemma1 one can save them by hitting a switch that will divert the trolley onto a side-track, where it will kill only one person. In the footbridge dilemma one can save them by pushing someone off a footbridge and into the trolley’s path, killing him, but stopping the trolley. Most people approve of the five-for-one tradeoff in the switch dilemma, but not in the footbridge dilemma (Cushman et al., 2006, Greene et al., 2001, Petrinovich et al., 1993).
What explains this pattern of judgment? Neuroimaging (Greene et al., 2001, Greene et al., 2004), lesion (Ciaramelli et al., 2007, Koenigs et al., 2007, Mendez et al., 2005), and behavioral (Bartels, 2008, Greene et al., 2008, Valdesolo and DeSteno, 2006) studies indicate that people respond differently to these two cases because the action in the footbridge dilemma elicits a stronger negative emotional response. But what features of this action elicit this response? Recent studies implicate two general factors. First, following Aquinas (2006), many appeal to intention and, more specifically, the distinction between harm intended as a means to a greater good (as in the footbridge dilemma) and harm that is a foreseen but “unintended” side-effect of achieving a greater good (as in the switch dilemma) (Cushman et al., 2006, Hauser et al., 2007, Mikhail, 2000, Schaich Borg et al., 2006). Second, many studies appeal to varying forms of “directness” or “personalness,” including physical contact between agent and victim (Cushman et al., 2006), the locus of intervention (victim vs. threat) in the action’s underlying causal model (Waldmann & Dieterich, 2007), whether the action involves deflecting an existing threat (Greene et al., 2001), and whether the harmful action is mechanically mediated (Moore et al., 2008, Royzman and Baron, 2002). The aim of this paper is to integrate these two lines of research.
We present two experiments examining a directness/personalness factor that we call personal force. An agent applies personal force to another when the force that directly impacts the other is generated by the agent’s muscles, as when one pushes another with one’s hands or with a rigid object. Thus, applications of personal force, so defined, cannot be mediated by mechanisms that respond to the agent’s muscular force by releasing or generating a different kind of force and applying it to the other person. Although all voluntary actions that affect others involve muscular contractions, they do not necessarily involve the application of personal force to another person. For example, firing a gun at someone or dropping a weight onto someone by releasing a lever do not involve the application of personal force because the victims in such cases are directly impacted by a force that is distinct from the agent’s muscular force, i.e. by the force of an explosion or gravity. The cases of direct harm examined by Royzman and Baron (2002) are not so direct as to involve the application of personal force. The direct/indirect distinction described by Moore and colleagues (2008) is similar to the distinction drawn here between personal and impersonal force, but Moore and colleagues do not systematically distinguish between physical contact and personal force.
Experiments 2 Experiment 1a, 3 Experiment 1b aim to document the influence of personal force, contrasting its effect with those of physical contact (1a–b) and spatial proximity (1a) between agent and victim. Experiment 1a also introduces a method for controlling for effects of unconscious realism, i.e. a tendency to unconsciously replace a moral dilemma’s unrealistic assumptions with more realistic ones. (“Trying to stop a trolley with a person is unlikely to work.”) Experiments 4 Experiment 2a, 5 Experiment 2b examine the interaction between personal force and intention. More specifically, we ask whether the effect of personal force depends on intention and vice versa.
Section snippets
Experiment 1a
We compared four versions of the footbridge dilemma to isolate the effects of spatial proximity, physical contact, and personal force on moral judgments concerning harmful actions. We also tested the unconscious realism hypothesis by controlling for subjects’ real-world expectations.
Experiment 1b
To ensure that the results concerning personal force and physical contact observed in Experiment 1a generalize to other contexts, we conducted an additional experiment using a different set of moral dilemmas, as well as a different rating scale.
Experiment 2a
This experiment examined the independent effects of personal force and intention and, most critically, their interaction, by comparing four dilemmas using a 2 (personal force absent vs. present) × 2 (means vs. side-effect) design.
Experiment 2b
To ensure that the main results observed in Experiment 2a generalize to other contexts, we recoded and reanalyzed the data from Cushman et al. (2006). More specifically, we examined the moral permissibility ratings for the 19 moral dilemmas involving actions (rather than omissions), including five dilemmas in which the harm is caused as a means without personal force (Means–noPf), six dilemmas in which the harm is caused as a side-effect without personal force (SE–noPf), three dilemmas in which
Discussion
In two sets of experiments, harmful actions were judged to be less morally acceptable when the agent applied personal force to the victim. In Experiments 2 Experiment 1a, 3 Experiment 1b the effect of personal force was documented and distinguished from effects of physical contact (Cushman et al., 2006) and spatial proximity (1a only), which were not significant. Experiments 4 Experiment 2a, 5 Experiment 2b revealed that personal force interacts with intention, such that the personal force
Acknowledgements
We thank Andrew Conway, Daniel Gilbert, Andrea Heberlein, Wendy Mendes, and Daniel Wegner for their assistance. This work was supported by the NSF (BCS-0351996) and NIH (MH067410).
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