On September 11, 2001, members of the terrorist group al-Qaeda hijacked two airplanes and crashed them into the twin towers of the World Trade Center in New York, killing close to 3000 people and injuring more than 6000 others. This horrifying event ignited heated debates about whether it would be acceptable to shoot down hijacked passenger planes to prevent terrorists from crashing them into densely populated areas. Whereas some argued that it would be morally acceptable to actively kill innocent passengers on a hijacked plane to prevent greater harm, others argued that such actions would be immoral regardless of how many lives would be saved.

The conflicting views in this debate can be linked to two moral principles that play a central role in research on moral judgment. First, the principle of deontology, often associated with the moral philosophy of Immanuel Kant, emphasizes the irrevocable universality of rights and duties. From a deontological view, the moral status of a given action depends on its consistency with moral norms. That is, a given action is acceptable if it is consistent with a set of moral norms, but it is unacceptable if it is inconsistent with this set of moral norms (e.g., shooting a hijacked passenger plane is unacceptable from a deontological view, because it violates the norm that one should not kill innocent people). Second, the principle of utilitarianism, often associated with the moral philosophy of John Stuart Mill, emphasizes actions that bring about the greatest good. From a utilitarian view, the moral status of a given action depends on its consequences for overall well-being. To the extent that a given action increases overall well-being, it is deemed morally acceptable. Conversely, if the same action decreases overall well-being, it is deemed morally unacceptable (e.g., shooting a hijacked passenger plane is acceptable from a utilitarian view to the extent that it prevents the potential death of a larger number of people).

To understand the psychological roots of conflicting views in moral debates, a substantial body of research has investigated personal and situational factors that influence people’s preference for utilitarian versus deontological judgments in moral dilemmas where the two principles have conflicting implications (e.g., Suter & Hertwig, 2011). In an attempt to provide deeper insights into the determinants of moral preferences, several studies aimed to identify their neural underpinnings using neuroimaging (e.g., Greene, Sommerville, Nystrom, Darley, & Cohen, 2001) and patients with focal brain lesions (e.g., Koenigs, Young, Adolphs, Hause, Tranel, Cushman, Hauser, & Damasio, 2007). Expanding on the latter work, there has been an increasing interest in the contribution of neuroendocrine factors to moral dilemma judgments (e.g., Carney & Mason, 2010). This interest is rooted in the idea that neuroendocrine factors can influence moral judgments in a fundamental way by regulating brain activity in areas that have been associated with moral judgments (e.g., Chen, Decety, Huang, Chen, & Cheng, 2016). Moreover, moral judgments have been claimed to be at least partly rooted in evolved psychological mechanisms related to reproduction and cooperation among conspecifics (e.g., Sacco, Brown, Lustgraaf, & Hugenberg, 2017). To the extent that neuroendocrine processes play a central role in regulating these mechanisms (Narvaez, 2014), a multi-level approach that integrates social, psychological, neural, and endocrine factors promises a deeper theoretical understanding of moral judgments compared to research that focuses exclusively on behavioral responses and associated brain regions (Haidt, 2008). Such an integrative approach is essential for understanding conflicting views in moral debates (e.g., about whether it is acceptable to shoot down a hijacked passenger plane) by identifying their origin and the conditions under which they may be responsive or resistant to persuasive arguments (Stanley, Dougherty, Yang, Henne, & DeBrigard, in press).

Expanding on the need for a multi-level approach to understanding moral judgments, this preregistered study investigates the effect of the steroid hormone testosterone on moral dilemma judgments by experimentally manipulating testosterone levels through double-blind administration of either testosterone or placebo. Compared to other hormones with downstream effects on decision-making, testosterone is a prime candidate for understanding neuroendocrine effects on moral judgments, in that elevated levels of testosterone have been linked with various outcomes that are relevant for moral judgments. Based on earlier research suggesting that higher levels of testosterone are associated with a stronger preference for utilitarian over deontological judgments (e.g., Carney & Mason, 2010), the main goal of the current work is to provide deeper insights into how testosterone influences moral dilemma judgments. Toward this end, the current work uses a mathematical model that disentangles three functionally distinct determinants of moral dilemma judgments: (a) sensitivity to consequences in a utilitarian sense, (b) sensitivity to moral norms in a deontological sense, and (c) general preference for inaction versus action regardless of consequences and norms (Gawronski, Armstrong, Conway, Friesdorf, & Hütter, 2017). Using the 9/11 dilemma as an illustrative example, we are interested in whether testosterone increases the perceived acceptability of shooting down a hijacked passenger plane to prevent greater harm, and if so, whether this increase is driven by an increased sensitivity to consequences (i.e., number of lives saved), a reduced sensitivity to moral norms (i.e., norm that one should not kill), or an increased preference for action responses regardless of consequences and moral norms.

A manuscript on the preregistered study has received in principle acceptance (IPA) by Nature Human Behaviour. The EASP Preregistered Research Grant has been used to cover approximately half of the expenditures for the testosterone and placebo nasal sprays that are administered to participants in the study. The data collection for a total of 200 participants is still ongoing (180 participants as of May 4, 2018, the last day of the spring term at UT Austin) and will be finished in the fall 2018. 

References

• Chen, C., Decety, J., Huang, P.-C., Chen, C.-Y., & Cheng, Y. (2016). Testosterone administration in females modulates moral judgment and patterns of brain activation and functional connectivity. Human Brain Mapping, 37, 3417-3430.
• Gawronski, B., Armstrong, J., Conway, P., Friesdorf, R., & Hütter, M. (2017). Consequences, norms, and generalized inaction in moral dilemmas: The CNI model of moral decision-making. Journal of Personality and Social Psychology, 113, 343-376.
• Greene, J. D., Sommerville, R. B., Nystrom, L. E., Darley, J. M., & Cohen, J. D. (2001). An fMRI investigation of emotional engagement in moral judgment. Science, 293, 2105-2108.
• Haidt, J. (2008). Morality. Perspectives on Psychological Science, 3, 65-72.
• Koenigs, M., Young, L., Adolphs, R., Tranel, D., Cushman, F., Hauser, M., & Damasio, A. (2007). Damage to the prefrontal cortex increases utilitarian moral judgments. Nature, 446, 908-911.
• Narvaez, D. (2014). Neurobiology and the development of human morality: Evolution, culture, and wisdom. New York: Norton.
• Sacco, D. F., Brown, M., Lustgraaf, C. J. N., & Hugenberg, K. (2017). The adaptive utility of deontology: Deontological moral decision-making fosters perceptions of trust and likeability. Evolutionary Psychological Science, 3, 125-132.
• Stanley, M. L., Dougherty, A. M., Yang, B. W., Henne, P., & De Brigard, F. (in press). Reasons probably won’t change your mind: The role of reasons in revision moral decisions. Journal of Experimental Psychology: General.
• Suter, R. S., & Hertwig, R. (2011). Time and moral judgment. Cognition, 119, 454-458.