Metaphors influence the way we think. In a paper in PLoS ONE published today, Paul Thibodeau and Lera Boroditsky, psychologists at Stanford University in California, show that people approve of differing responses to crime when it is presented as either a 'beast' or a 'virus' ravaging society1. In the former case they are most likely to call for strong law enforcement, whereas in the latter they are more open to solutions such as rehabilitation and the understanding of root causes.

Perhaps the most striking aspect of this study is that the participants were unaware of the how the metaphorical context affected their reasoning. Instead of acknowledging the image's effect, they found ways to rationalize their decisions on the basis of seemingly objective information such as statistics. "Far from being mere rhetorical flourishes," say Thibodeau and Boroditsky, "metaphors have profound influences on how we conceptualize and act with respect to important societal issues."

To have this demonstrated and quantified is valuable — not least because it underlines something that politicians and their advisers have never doubted. If there is a spin doctor or speechwriter who does not already recognize that metaphors sway opinion, it is a mystery how they ever got the job.

It isn't hard to see why 'crime as wild beast of prey' encourages people to think about how to cage or kill it, whereas 'crime as virus' fosters more eagerness for 'scientific' understanding of causes. But too rarely are such metaphors interrogated at a deeper level.

In both these cases, crime is presented as a (malevolent) force of nature, outside human agency. Whether beast or virus, the criminal is not like us — is not human. By the same token, a 'war on drugs' or a 'war on terror' is not just an emotive image, but deploys a militaristic narrative that bears little relation to reality.

Misleading mentality

In literature, metaphor serves poetic ends; in politics, it is a (subtly manipulative) argument by analogy. But in science, metaphor is widely considered an essential tool for understanding. So where then does this latest work leave us?

Whereas the example of crime used here imputes natural agency to human actions, science generally invokes metaphors the other way around: natural processes are described as if they result from intention. This anthropomorphizing tendency was dubbed the 'pathetic fallacy' by the nineteenth-century critic John Ruskin, although it had also been noted by the scientist and philosopher Francis Bacon, two centuries earlier.

Which one is more like crime? Credit: Photos 12 / Alamy, MEDICAL RF.COM/SPL

The pathetic fallacy is an ingrained and profoundly influential habit, especially in biology26, where intimations of intelligent agency seem irresistible even to those who deplore them. Most famous in this respect is the 'selfish gene' proposed by biologist Richard Dawkins in his 1976 book of that title. Dawkins' metaphor is apt and understandable almost to the point of inevitability, given the idea that he strove to convey. But its problems go well beyond the fact that genes are of course not selfish in the way that people are (which is to say, they are not selfish at all).

The 'selfish gene' props up the whole notion of a Darwinian world that is uncaring to the point of being positively nasty: an image that has sometimes provoked resistance to the sciences in general and natural selection in particular. And as Denis Noble, a physiologist at the University of Oxford, UK, has compellingly argued, the idea that genes are selfish is totally unnecessary to an understanding of how they work, and is in some ways misleading7.

But it is no better to talk instead of the 'cooperative gene', which is equally value-laden and misinformative. Genes are not selfish or cooperative any more than they are happy or short-tempered. It is the concept of scientific metaphor in general that is problematic8,9.

On guard

Books of life, junk DNA, DNA barcodes: all these images can and have distorted the picture, not least because scientists themselves sometimes forget that they are metaphors. And when the science moves on — when we discover that the genome is nothing like a book or blueprint — the metaphors tend, nonetheless, to stick. The more vivid the image, the more dangerously seductive and resistant to change it is.

Thibodeau and Boroditsky give us new cause to be wary, for they show how unconsciously metaphors colour our reasoning. This seems likely to be as true in science — especially a science as emotive as genetics — as it is in social and political discourse.

Most scientists would probably agree with Robert Root-Bernstein, a physiologist at Michigan State University in East Lansing, that "metaphors are essential to doing and teaching science"10. They might also sympathize with Paul Hebert, a biologist at the University of Guelph in Canada, who responded to criticisms of his 'DNA barcoding' metaphor11 by asking, "Why would we want to be so scientifically proper as to make our science tedious?"3

But the need for metaphor in science stands at risk of becoming dogma. Maybe we are too eager to find a neat metaphor rather than just explain what is going on as clearly and honestly as we can. We might want to recognize that some scientific concepts are "a reality beyond metaphor", as Nobel laureate David Baltimore, a biologist at the California Institute of Technology in Pasadena, has said of DNA3. At the very least, metaphor should be admitted into science only after strict examination. We ought to heed the warning of pioneering cyberneticists Arturo Rosenblueth and Norbert Wiener that "the price of metaphor is eternal vigilance"12.