The Origins and Nature of Human Moral Perception

Steven Pinker has written an overview of scientific research into the origins and nature of human moral perception for the New York Times.

This variety of inquiry into ethics differs from the traditional philosophical approach. The idea here is that the human experience of moral judgment can be usefully analyzed without reference to some theoretical objective moral standard — thereby sidestepping the traditional philosophical quagmires.

Moral judgment, in this school of thought, is a variety of sensation: a subjective qualitative experience that doesn’t have a qualitative counterpart in the objective world — in the same way that there is a continuous spectrum of electromagnetic frequencies in the objective world, but the sensation of color only exists in the subjective world.

Or, perhaps more closely analogous, “disgust” is a mental evaluation of the state of the world, but not a characteristic of that world — only a state of the mind that evaluates it.

If you look at morality in this way, you can go on to design experiments that show how people morally evaluate scenarios, what their brains do when they do so, and how this correlates with their behavior. And you can make educated guesses for how natural selection might have favored certain varieties of moral evaluation in our ancestors.

The promise of this approach is that you aren’t just arguing ethical philosophy (which can seem pretty fruitless), but you’re actually collecting data and testing hypotheses — mmmm… the delicious taste of Science!


Here is the worry. The scientific outlook has taught us that some parts of our subjective experience are products of our biological makeup and have no objective counterpart in the world. The qualitative difference between red and green, the tastiness of fruit and foulness of carrion, the scariness of heights and prettiness of flowers are design features of our common nervous system, and if our species had evolved in a different ecosystem or if we were missing a few genes, our reactions could go the other way. Now, if the distinction between right and wrong is also a product of brain wiring, why should we believe it is any more real than the distinction between red and green? And if it is just a collective hallucination, how could we argue that evils like genocide and slavery are wrong for everyone, rather than just distasteful to us?

It may be fruitful for us to discover why certain people under certain circumstances are morally repulsed by genocide, and other people under other circumstances are not, but the reason people dive into the philosophical quagmires rather than just leaving this to the scientists is that they’d like to go one step further and say that, in addition, one of those moral evaluations of genocide is the correct one, in much the same way as a mathematical truth is not just a point-of-view.

A scientific, descriptive understanding of moral sensations seems to leave something out. It threatens to reduce ethics to an arbitrary drive evolution has planted in us for reasons that have more to do with our dead ancestors than the living neighbors we practice it on. It seems to pull ethics outside of the realm of argument and make a mere phenomenon of it.

But even at this extreme, the consequences aren’t quite so bad as this. Note that people sometimes critically examine their instinctual evaluations and find them to be irrational and in need of rational augmentation. See, for instance, the “five second rule” by which food that has just been dropped to the floor moves from the safe-to-eat category into the too-vile-to-pass-our-lips category after a brief passage of time. This rule, or something like it, is something that many of us feel to be true, viscerally, but know to be hogwash, epidemiologically.

It isn’t difficult to believe that this feeling of disgust over dropped food is probably a heuristic in the form of a feeling — one that evolved to protect us from dangerously contaminated food — and that dropped food doesn’t become inherently or objectively disgusting when the subjective edibility timer runs out. But knowing the purpose and origins of our instinctual perception of disgust — knowing that it’s a mere phenomenon and an artifact of how evolution shaped our brains — doesn’t end the story, but provides a jumping-off point for rational refinement of the original sub-rational evaluation.

It’s possible that the same is true of investigations into moral evaluation. Most of us have a semi-rational ethical worldview that we like to think we conform to, and a moral “feeling” apparatus that operates, more-or-less in parallel, at a pre-rational or even subconscious level. The more we know about how that apparatus operates, the more we can anticipate when and how it will conflict with the ethics we would choose consciously and rationally. Then we can prepare and adjust accordingly.