Joshua D. Greene
Assistant Professor
Department of Psychology
Harvard University
William James Hall 1480
33 Kirkland Street
Cambridge, MA 02138


email: jgreene-at-wjh-dot-harvard-dot-edu (replace "-at-" and "-dot-" as usual)
phone: (617) 495-3898
office: William James Hall 1480

CV (PDF)

For more information about my research and collaborators, please visit the Moral Cognition Lab webpage.

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Research and Background
I study moral judgment and decision-making using behavioral experiments, functional neuroimaging (fMRI), and other neuroscientific methods.  The goal of my research is to understand how moral judgments are shaped by automatic processes (such as emotional “gut reactions”) and controlled cognitive processes (such as reasoning and self-control).  Much of  my current work is aimed at understanding these automatic and controlled processes in more detailed funcitonal terms.  I also have a new line of research examining the cognitive nature of honesty and dishonesty, which doubles as research on brain-based lie-detection.  Much of my research is motivated by normative philosophical questions.  I am currently writing a book about the moral implications of our emerging scientific understanding of morality.


Emotion and Reason in Moral Judgment
 
Rationalist philosophers such as Plato and Kant conceived of mature moral judgment as a rational enterprise, as a matter of appreciating abstract reasons that in themselves provide direction and motivation.  In contrast to these philospohers, "sentimentalist" philosophers such as David Hume and Adam Smith argued that emotions are the primary basis for moral judgment.  In more recent years, the rationalist banner has been carried by developmental psychologists such as Lawrence Kohlberg.  Likewise, some contemporary researchers, most notably Jonathan Haidt, have emphasized the importance of emotion in moral judgment.  I think that emotion and reason are both important forces in moral judgment and that their respective influences have been widely misunderstood.

   More specifically, I have proposed a "dual-process" theory of moral judgment according to which characteristcically deontological moral judgments (judgments associated with concerns for "rights" and "duties") are driven by automatic emotional responses, while characteristically utilitarian or consequentialist moral judgments (judgments aimed at promoting the "greater good") are driven by more controlled cognitive processes.  If I'm right, the tension between deontological and consequentialist moral philosohies reflects an underlying tension between dissociable systems in the brain.  Many of my experiments employ moral dilemmas, adapted from the philosophical literature, that are designed to exploit this tension and reveal its psychological and neural underpinnings.


Moral Dilemmas and the "Trolley Problem"
 
My main line of experimental research began as an attempt to understand the "Trolley Problem," which was originally posed by the philosophers Philippa Foot and Judith Jarvis Thomson. 

    First, we have the switch dilemma:  A runaway trolley is hurtling down the tracks toward five people who will be killed if it proceeds on its present course. You can save these five people by diverting the trolley onto a different set of tracks, one that has only one person on it, but if you do this that person will be killed. Is it morally permissible to turn the trolley and thus prevent five deaths at the cost of one?   Most people say "Yes."

   Then we have the footbirdge dilemma:  Once again, the trolley is headed for five people. You are standing next to a large man on a footbridge spanning the tracks. The only way to save the five people is to push this man off the footbridge and into the path of the trolley.  Is that morally permissible?  Most people say "No."

    These two cases create a puzzle for moral philosophers:  What makes it okay to sacrifice one person to save five others in the switch case but not in the footbridge case?  There is also a psychological puzzle here:  How does everyone know (or "know") that it's okay to turn the trolley but not okay to push the man off the footbridge?

Sidebar: 3) A surgeon has 5 patients who all need organ transplants (from exposure to radiation let's say, they are not smokers or fast food eaters or anything of that nature). One needs a heart, one needs a lung, and so on. They will all die within a day if they do not receive the transplants, but the surgeon himself is so skilled that if he is just able to find the organs, his 5 patients will all certainly live. A single healthy man comes into the office for a checkup that day; should the surgeon kill him and harvest his organs to save the other 5?

   According to my dual-process theory of moral judgment, our differing responses to these two dilemmas reflect the operations of at least two distinct psychological/neural systems.  On the one hand, there is a system that tends to think about both of these problems in utilitarian terms:  Better to save as many lives as possible.  The operations of this system are more controlled, perhaps more reasoned, and tend to be relatively unemotional.  This system appears to depend on the dorsolateral prefrontal cortex, a part of the brain associated with "cognitive control" and reasoning.

  On the other hand, there is a different neural system that responds very differently to these two dilemmas.  This system typically responds with a relatively strong, negative emotional response to the action in the footbridge dilemma, but not to the action in the switch dilemma.  When this more emotional system is engaged, its responses tend to dominate people's judgments, explaining why people tend to make utilitarian judgments in response to the switch dilemma, but not in response to the footbridge dilemma.

   If you make the utilitarian judgment sufficiently attractive, you can elicit a prolonged competition between these two systems.  Consider the crying baby dilemma:  It's war time, and you are hiding in a basement with several other people.  The enemy soldiers are outside.  Your baby starts to cry loudly, and if nothing is done the soldiers will find you and kill you, your baby, and everyone else in the basement.  The only way to prevent this from happening is to cover your baby's mouth, but if you do this the baby will smother to death.  Is it morally permissible to do this?

   According to the dual-process theory, this dilemma is difficult because it, like the footbridge dilemma elicits a strong negative emotional response ("Don't kill the baby!"), while at the same time eliciting a comparably compelling utilitarain response from the other system ("But if you don't kill the baby, everyone dies.")  Difficult dilemmas like this one tend to elicit increased activity in the anterior cingulate cortex, a brain region associated with "response conflict."  And when people make utilitarian judgments in response to these difficult dilemas, they exhibit increased activity in anterior regions of the dorsolateral prefrontal cortex.


The Moral Significance of Moral Psychology

My interest in understanding how the moral mind/brain works is in part driven by good-old-fashioned curiosity, but I also believe that we can uses a scientific understanding of morality to make the world better.  As everyone knows, we humans are beset by a number of serious social problems: war, terrorism, the destruction of the environment, etc.  Many people think that the cure for these ills is a heaping helping of common sense morality:  "If only people everywhere would do what they know, deep down, is right, we'd all get along."

    I believe that the opposite is true, that the aforementioned problems are a product of well-intentioned people abiding by their respective common senses and that the only long-run solution to these problems is for people to develop a healthy distrust of moral common sense.  This is largely because our social instincts were not designed for the modern world.  Nor, for that matter, were they designed to promote peace and happiness in the world for which they were designed, the world of our hunter-gatherer ancestors.
   
    My goal as a scientist, then, is to reveal our moral thinking for what it is:  a complex hodgepodge of emotional responses and rational (re)constructions, shaped by both genetic and cultural influences, that do some things well and other things extremely poorly.  My hope is that by understanding how we think, we can teach ourselves to think better, i.e. in ways that better serve the needs of humanity as a whole.
   
    For a short introduction to some of these ideas, you can download this article.  For a longer, and more philosophically contentious, presentation, I recommend this article.  Then there is my philosophy dissertation, which you are welcome to slog through.  Finally, I am writing a book about these issues, which I expect to be published in 2011.  I also have a related paper about the problem of free will and legal responsibility (co-authored with my former advisor, Jonathan Cohen).



Book
Greene, J.D. (forthcoming, 2011).  The Moral Brain and How to Use It.  Penguin Group, New York.  My forthcoming book is about the moral and social implications of our emerging scientific understanding of morality.  It is a much revised and expanded version of my philosophy dissertation.


Dissertation

Greene, J. D. (2002). The Terrible, Horrible, No Good, Very Bad Truth About Morality and What To Do About It. Department of Philosophy, Princeton University. (advised by David Lewis and Gilbert Harman)  PDF


Journal Articles

Cushman, F.A., Murray, D., Gordon-McKeon, S., Wharton, S., Greene, J.D. (in prep) Why is ‘killing’ worse than ‘letting die?’: Evidence from functional neuroimaging.

Shenhav, A.S., Greene, J.D. (in prep) Utilitarian calculations, emotional assessments, and integrative moral judgments: Dissociating neural systems underlying moral judgment.

Greene, J.D., Lowenberg, K., Nystrom, L.E., and Cohen, J.D. (in prep) Neural dissociation between affective and cognitive moral disapproval.

Shariff, A.F., Greene, J.D., Schooler, J.W., (in prep)  His brain made him do it: Encouraging a mechanistic worldview reduces punishment..

Greene, J.D., Lowenberg, K., Nystrom, L.E., Darley, J.M., and Cohen, J.D. (in prep) Duty vs. the greater good: dissociable neural bases of deontological and utilitarian moral judgment in the context of keeping and breaking promises.

Baron, J., Ritov, I., and Greene, J.D. (submitted) The duty to support nationalistic policies.

Shenhav, A.S., Greene, J.D. (2010).  Moral judgments recruit domain-general valuation mechanisms to integrate representations of probability and magnitude.  Neuron, 67, 667-677. PDF

Bazerman, M.H. and Greene, J.D. (2010).  In favor of clear thinking:  Incorporating moral rules into wise cost-benefit analysis.  Perspectives on Psychological Science, 5(2), 209-212. PDF

Paxton, J.M., Greene, J.D., (2010)  Moral reasoning: Hints and allegations. Topics in Cognitive Science.  DOI: 10.1111/j.1756-8765.2010.01096.x PDF

Greene, J.D., Paxton, J.M. (2009) Patterns of neural activity associated with honest and dishonest moral decisions.  Proceedings of the National Academy of Sciences USA, Vol. 106, No. 30, 12506-12511. PDF

Paharia, N., Kassam, K.S., Greene, J.D., Bazerman, M.H. (2009)  Dirty work, clean hands: the moral psychology of indirect agency.  Organizational Behavior and Human Decision Processes, 109, 134-141. PDF

Greene, J.D., Cushman, F.A., Stewart. L.E., Lowenberg, K., Nystrom, L.E., and Cohen, J.D. (2009) Pushing moral buttons: The interaction between personal force and intention in moral judgment.  Cognition, Vol. 111 (3), 364-371. PDF Supplementary Materials

Greene, J.D. (2009) Dual-process morality and the personal/impersonal distinction: A reply to McGuire, Langdon, Coltheart, and Mackenzie.  Journal of Experimental Social Psychology, Vol. 45 (3), 581-584. PDF

Greene, J.D., Morelli, S.A., Lowenberg, K., Nystrom, L.E., Cohen, J.D. (2008) Cognitive load selectively interferes with utilitarian moral judgment.  Cognition, Vol. 107, 1144-1154. PDF Supplementary Materials

Greene, J.D. (2007)  Why are VMPFC patients more utilitarian?: A dual-process theory of moral judgment explains.  Trends in Cognitive Sciences. Vol 11, No. 8, 322-323. PDF

Greene, J. D. , Cohen J. D. (2004) For the law, neuroscience changes nothing and everything. Philosophical Transactions of the Royal Society of London B, (Special Issue on Law and the Brain), 359, 1775-17785.  PDF
 
Greene, J.D., Nystrom, L.E., Engell, A.D., Darley, J.M., Cohen, J.D. (2004)  The neural bases of cognitive conflict and control in moral judgment. Neuron, Vol. 44, 389-400.  PDF
 
Greene, J.D. (2003) From neural "is" to moral "ought": what are the moral implications of neuroscientific moral psychology?  Nature Reviews Neuroscience, Vol. 4, 847-850.  PDF
 
Greene, J. and Haidt, J. (2002) How (and where) does moral judgment work?  Trends in Cognitive Sciences, 6(12), 517-523.  PDF
 
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, Vol. 293, Sept. 14, 2001, 2105-2108.  PDF
 
Greene, J.D., Baron, J. (2001).  Intuitions about declining marginal utility.  Journal of Behavioral Decision Making, 14, 243-255.  PDF
 
Baron, J., Greene, J.D. (1996). Determinants of insensitivity to quantity in valuation of public goods. Journal of Experimental Psychology: Applied, 2, 107-125.  PDF



Book Chapters
Cushman, F.A., and Greene, J.D. (in press)  The philosopher in the theater, in The Social psychology of morality: The origins of good and evil, M. Mikulincer, P.R. Shaver, Eds.  APA Press. PDF

Cushman, F.A. and Greene, J.D. (in press) Finding faults: How moral dilemmas reveal cognitive structure, in The Handbook of Social Neuroscience, Jean Decety and John Cacioppo, Eds.  Oxford University Press. PDF

Cushman, F., Young, L., Greene, J.D. (in press)  Our mutli-system moral psychology:  Towards a consensus view, in The Oxford Handbook of Moral Psychology, J. Doris, G. Harman, S. Nichols, J. Prinz, W. Sinnott-Armstrong, S. Stich, Eds.  Oxford University Press. PDF

Greene, J. D. (in press)  Social neuroscience and the soul's last stand, in Social Neuroscience: Toward Understanding the Underpinnings of the Social Mind, A. Todorov, S. Fiske, and D. Prentice, Eds.  Oxford University Press, New York. PDF

Greene, J.D. (2009) The cognitive neuroscience of moral judgment, in The Cognitive Neurosciences IV, M.S. Gazzaniga, Ed.  MIT Press, Cambridge, MA. PDF

Greene, J.D. (2009)  Fruit flies of the moral mind, in What's Next: Dispatches from the Future of Science, M. Brockman, Ed., Vintage, New York.

Greene, J. D. (2007). The secret joke of Kant's soul, in Moral Psychology, Vol. 3: The Neuroscience of Morality: Emotion, Disease, and Development, W. Sinnott-Armstrong, Ed., MIT Press, Cambridge, MA. PDF

McClure, S.M., Botvinick, M.M., Yeung, N., Greene, J.D., Cohen, J.D.  (2007). Conflict monitoring in conflict-emotion competition, in Handbook of Emotion Regulation, J.J. Gross Ed., Guilford Press, New York.
 
Greene, J. D. , Cohen J. D. (2006), For the law, neuroscience changes nothing and everything, in Law and the Brain, S. Zeki and O. Goodenough, Eds., Oxford University Press, New York. PDF (journal version)
 
Greene, J. (2005). Emotion and cognition in moral judgment: evidence from neuroimaging, in Neurobiology of Human Values, J.P. Changeux, A.R. Damasio, W. Singer, and Y. Christen, Eds., Springer-Verlag, Berlin.
 
Greene, J. (2005). Cognitive neuroscience and the structure of the moral mind, in The Innate Mind: Structure and Contents, S. Laurence, P. Carruthers,. and S. Stich. Eds., Oxford University Press, New York.  PDF

Bound

I think morality, while continually adapting to circumstances (i.e.; its relatve), is based on Darwinian principles. While particular moral issues can be ambiguous, the ultimate purpose is to increase the chances of the survival of our species. Generally that means one has moral responsibilities towards oneself, one's family, community, and country. Often a balance must be sought between them. Often the morally correct action is symbolic rather than tangible.

In the example I would judge it proper to save the greater number of people because utilitarianism is the basic principle behind survival. That could be over-ruled by extenuating circumstances, such as if the lone person was a close relative or someone who was exceptionally important to the community or the country. A child might qualify because children are symbolic of our future.

I think it would be immoral to push the fat man because that would lead to undermining relationships of trust within our society. If the choice is between killing the fat man our the lone worker, and all else being equal, its more important to be able to trust the person standing next to you. There's all kinds of ways to complicate the decision though. If there were 6 people on one track and 20 people on the other it might warrant pushing the fat man as well as going over ones self.

The question of the surgeon should be a no brainer. Its not at all like the other two situations because the doctor is in a professional relationship of trust with his patient. The price of saving the 5 individuals is not simply the one life he would sacrifice, but the trust his profession must preserve at all costs.

What if the fat man decided to switch the tracks and kill the lone worker? Should you try to prevent him from doing so? Should you switch it back to save the one and sacrifice the other five?

As somebody who thinks it's wrong to pull the lever...THAT is a good question I hadn't thought of.

If hitting the switch means I murdered the lone guy, then not hitting the switch means I murdered the group of workers.
I don't think so at all.

If you do not hit the switch you let 5 people die. If you pull the switch you directly cause somebody's death. There is a large difference between letting somebody die, and killing them.

Since you still hold to the idea that #1 is different from #2/3 on the grounds that the latter two have you "commit murder", I would like to put another scenario to you:

There are 5 people who need organ transplants to survive. You are an outside observer, and have a lever next to you which, when pulled, will activate a robot which will dissect a healthy man and use his organs to save the other 5.

Do you view this as different from scenario #1? And how/why?