Psychic Numbing (originally posted at OSU Press)

Author: Paul Slovic

The human mind is capable of astonishing feats of creative problem solving and technological wizardry. And we are good with numbers, too, when we think slowly and carefully about them—witness the three-billion-mile voyage the New Horizons spacecraft just made in its close encounter with Pluto.

But, most of the time, we let our brain calculate for us in a fast, intuitive mode of thinking where answers come, not as numbers or numerical comparisons of benefits and costs, but rather as feelings—good, bad, attractive, unattractive, likable or not, etc. Psychologists refer to these feelings as “affect.” When the objects of our attention are people, or other creatures in distress, these feelings represent what Polish poet Zbigniew Herbert has called “the arithmetic of compassion.”

Unfortunately, when we let our intuitive feelings function as our “moral compass,” the arithmetic of compassion is often faulty, in ways that Scott and I describe in the early chapters of Numbers and Nerves. Evolution designed our faculties of vision and hearing to be most sensitive to faint sounds and dim images, to alert us quickly to subtle signs of impending danger. But a nervous system that is exquisitely sensitive to small phenomena cannot sustain that sensitivity as sound becomes louder and light becomes brighter. Doubling the sound or light energy of a stimulus does not double its perceived loudness or brightness. Remarkably, and unfortunately, a similar desensitization occurs when we rely on our quick intuitive feelings to judge the value of amounts of money or numbers of endangered lives. Finding 200 dollars does not make us twice as happy as finding 100, and hearing about 200 threatened lives does not distress us twice as much as the news of 100 does. In some circumstances, these 200 endangered lives may even feel less important than 100. A strange arithmetic, indeed—a form of “psychic numbing.”

The introduction to our book illustrates this desensitization with this four-photo display of candles, where every candle represents a life.

The first lit candle brightens the scene markedly. The second candle makes it a bit brighter, but not twice as much. Going from 30 candles in the third image to 31 in the fourth hardly seems to make a difference. In blunt terms, with this kind of thinking, the felt value of a life is not fixed. We often go to great lengths to protect a single person, even a single animal or a tree. But those individual lives feel less valuable as the number of other lives at risk increases. In such circumstances, our efforts to protect individuals similarly decrease.

One way to counter psychic numbing and better apprehend the scale of threats to humans, other species, and the planet more broadly may be to link faces, names, stories, and images to the statistics in vivid, multidimensional ways. In the latter sections of our book, we call on writers and visual artists to show how this might be done and why it is important in a world facing many challenges. You could say that our aim in creating this book has been to facilitate a more rational arithmetic of compassion.