Critical views of science in the news

The truth we'll doubt: Does the "decline effect" mean that all science is "truthy"?


As an old hippy I still get a kick out of anarchy, mayhem and challenges to authority. As a father, teacher, journalist and all-around pillar of the community, however, I've come to see the upside of the status quo more than I did in my carefree youth. So part of me thrills at WikiLeaks's assaults on government secrecy, whereas another part frets that forced transparency may subvert benign as well as malignant government actions.

I feel a similar ambivalence toward challenges to science's authority. Take, for example, "The Truth Wears Off," a bombshell that journalist Jonah Lehrer just detonated in The New Yorker. (The article is behind a pay-wall, but here is an abstract.) Lehrer reports on the "decline effect," the tendency of scientific claims to receive decreasing support over time. The term was coined by the parapsychologist J. B. Rhine in the 1930s to describe the apparent drop-off in extrasensory perception (ESP) of psychic subjects tested by Rhine for extended periods.

The likely explanation, of course, is that Rhine's subjects were never psychic; the initial finding of ESP was illusory, vanishing as Rhine's methods became more rigorous and his data more statistically significant. The decline effect is really a "decline of illusion," Lehrer explains, which "reminds us how difficult it is to prove anything." The decline effect has turned up in a host of fields, including not only squishy sciences like psychology, psychiatry, psychopharmacology and medical genetics, but even physics; measurements of the charge of electrons and a constant governing the decay of neutrons have exhibited the decline effect, according to Lehrer.

Lehrer attributes the effect to several common factors. First, a researcher stumbles on a dramatic correlation—say, between a new pharmaceutical and amelioration of schizophrenia—that actually stems not from causation but just from coincidence. The more dramatic the researcher's claim, the more likely he may be to get published and to obtain funding for more research. Other researchers jump on the bandwagon, doing follow-up studies that—because of the unconscious bias in favor of the initial claim—often corroborate it. Only gradually does counterevidence emerge, showing that the initial correlation stemmed not from causation but coincidence.

Consequently, science yields not truth but what comedy talk-show host Stephen Colbert calls "truthiness." None of this should surprise veteran science watchers—or anyone who's taken a course in the history or philosophy of science. I've whacked fields such as clinical psychology and behavioral genetics for churning out claims—A new and improved treatment for depression! A gene for liberalism!—that don't stand up to scrutiny. But Lehrer does a good job pulling together multiple strands into a unifying narrative of doubt. He cites the remarkable recent work of the epidemiologist John Ioaniddis, who has presented evidence that "most published research findings are false."

Lehrer also presents examples of the decline effect that were new to me. One is the link between physiological symmetry and sexual attraction in humans and other animals, which evolutionary psychologists have been touting for almost 20 years. Finally, the neo-Darwinian theory of human nature produced a not-completely obvious result! Except it didn't. A flurry of positive findings in the 1990s—Women have more orgasms when they couple with symmetrical guys!—gradually gave way to negative reports.

So why does Lehrer's article make me uneasy? First of all, early on he seems to suggest that the decline effect reflects changes in the phenomenon being measured, which is what Rhine meant by the term; only gradually does Lehrer make it clear that he attributes the effect to reporting bias. Some readers might still conclude that Lehrer is talking about an objective rather than subjective phenomenon; a colleague of mine was left with this impression after hearing Lehrer discuss "The Truth Wears Off" on National Public Radio. Moreover, Lehrer too quickly rules out fraud, especially in the case of reporting on drug trials, where the financial stakes are huge; he attributes the decline effect to "subtle omissions and unconscious misperceptions, as researchers struggle to make sense of their results."

But these are quibbles. My main complaint is that Lehrer makes science as a whole sound much "truthier" than it really is. His article was first pointed out to me by my friend Valerie, who believes in homeopathy and tarot cards. The article confirmed her suspicions that mainstream science and medicine may not be based on evidence any more solid than her supposedly (and IMHO, actually—sorry, Valerie) pseudoscientific beliefs. Lehrer's broad-brush critique will no doubt also cheer global-warming deniers, creationists, postmodernists and other pesky challengers of scientific orthodoxy.

Lehrer himself seems to have realized that he went too far. On his blog The Frontal Cortex, he dismisses the notion that "The Truth Wears Off" implicitly undermines the status of the theory of evolution by natural selection and global warming, which are "two of the most robust and widely tested theories of modern science." He also denies that he is "some sort of Derridean postmodernist, trying to turn publication bias into an excuse to not believe in anything."

But here is how Lehrer ends his article: "Just because an idea is true doesn't mean it can be proved. And just because an idea can be proved doesn't mean it's true. When the experiments are done, we still have to choose what to believe." This assertion is absurd. We may choose to believe in psychoanalysis rather than behaviorism, because both are equally flimsy. But the evidence is rock-solid for quantum mechanics, general relativity, the germ theory of infectious disease, the genetic code and many other building blocks of scientific knowledge, which have yielded applications that have transformed our world. There's nothing truthy about a hydrogen bomb.

If Lehrer didn't really mean that belief in a given scientific claim is always a matter of choice, why did he say it? He apparently decided, like many scientists, that truthiness would make a bigger splash than truth.

Image: Wikimedia Commons

The views expressed are those of the author and are not necessarily those of Scientific American.

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