Massimo Pigliucci
The Brain on Justice
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[The author is professor of evolutionary biology and philosophy at Stony Brook University in New York, a fellow of the American Association for the Advancement of Science, and author of Denying Evolution: Creationism, Scientism and the Nature of Science. ]
Justice, fairness, and the efficient distribution of resources do not seem at first the sort of topics that should interest a neurobiologist, at least not professionally. Philosophers have long discussed issues of justice and fairness, while economists compare strategies of distribution based on their expected efficiency in the markets. But science, philosophy, and economics are converging to re-evaluate how we think and act as social beings (see also my Thinking About Sience column, SI. November/December 2006)
The latest entry in this fascinating interdisciplinary field of inquiry is provided by a paper published in Science on May 23, 2008 by Ming Hsu, Cedric Anen, and Steven Quartz of the University of Illinois and the California Institute of Technology. Hsu and collaborators set out to identify the regions of the brain that are involved in the logically distinct tasks of assessing fairness and efficiency in the distribution of resources. The problem arises under common circumstances and presents us with the sort of choice that we have to make at several levels, from decisions affecting our own families to how we vote during elevations or allocate money to charity. For instance, to pick an example from the recently concluded Democratic primaries for president : is it better to provide health insurance to a large number of people (but not the entire population) at relatively high levels of coverage or to insure everyone, but at lower levels?
Philosophers, such as John Stuart Mill, who subscribe to a utilitarian ethics would argue that one needs to maximize the good of the majority - but not necessarily the totality - of people. Those who subscribe to a duty-bound ethics ( a so-called denotological system), like Immanuel Kant, would instead push for more fairness even at the cost of a suboptimal allocation to the majority of the population. Moreover, philosophers have disagreed on how we make this sort of decision, with rationalists like Plato and Kant arguing for the overriding role of reason countered by David Hume (and even, surprisingly, Adam Smith, the founder of modern economics) concluding that we ought to leave these decisions to our moral instincts, i.e., to our emotional responses.
Science cannot settle philosophical disputes directly, because there is a fundamental distinction between what is (matters of fact) and what ought to be (matters of value). Nonetheless, the researchers who authored the Science paper set out to see what human beings actually do (as opposed to what they should do), and the results are bound to make philosophers think for a while. Hsu and collaborators performed functional Magnetic Resonance Imaging of their subjects’ brains while they were considering the issue of how to allocate resources to children in an orphanage in Uganda. The experiment was designed so that the researchers could statistically control for the effect of fairness as distinct from optimality considerations while monitoring how the brain integrates the two types of information. The results were spectacularly clear.
A region called the putamen, which is a part of the basal ganglia, was particularly active when the subjects were considering the efficiency aspect of the problem at hand. However, when their attention shifted to the fairness question, the active region turned out to be the insula, which is part of the paralimbic zone. This, as it turns out, is in line with previous findings about these two regions of the brain : the insula was already known to be part of the emotional response system, while the putamen had been described as involved in rewarding computation and learning. The emerging picture from the neurobiological study, then, is that human beings approach issues of optimality using components of their rational brain, but fairness is judged by their emotional circuitry. Even more interesting is the finding by Hsu et al, that there is a third crucial area of the brain that was activated during the experiment, the so-called caudate/septual subgenual region. While this is also located in the basal ganglia, like the putamen, one of its functions appears to be integrating the information from the putamen and the insula and actually emerging with a decision that balances the optimality and allocation criteria. In other words, the brain’s rational and emotional circuitry come together in a way that can be thought of as the neurological equivalent of a philosophical debate among Mill, ant, Plato, and Hume!
What research like the study carried out by Hsu and collaborators tells us is not that science is about to take over philosophy, as biologist E.O. Wilson has famously advocated (see Thinking About Science. SI, March/April 2008). But rather that we are seeing an increasingly interdisciplinary approach to complex questions, with a broadening area of overlap between fields of inquiry. This requires some philosophical background on the part of scientists, as is in fact displayed at the beginning of the Science article, because philosophy helps to frame the question. At the same time, philosophers can no longer afford - if they ever could - to continue their debates independently of the discoveries of science, or they risk being left behind in the exciting quest to understand the nature of human moral decision making.
- Courtesy: Skeptical Inquirer - September - October, 2008.
