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There is a good-news-bad-news rhythm to the introduction of any pervasive new technology. With cellular telephones, for instance, the good news came with the explosive growth of the industry itself, which by November 1992 had recorded its 10 millionth customer. Three months later came the bad news: David Reynard, bereaved husband, appeared on “Larry King Live” with the remarkable accusation that cell-phone use had caused the brain tumor that killed his wife. Reynard, not surprisingly, was suing the cell-phone companies he held responsible. With that single anecdotal incident, Reynard set in motion a health scare that continues to play in the press and our societal subconscious to this day. If history is any indication, it will continue indefinitely. I can make this prediction free of concern about whether cell-phone use is truly carcinogenic. If it’s not, in fact, our anxiety-and the amount of press that fuels this anxiety-is likely to last considerably longer. Such is the nature of fear and the nature of science, and the inability of the latter to dispel the former.

The noteworthy aspect of fear is that its shelf life is considerably longer when the object of fear is a threshold phenomenon-invisible, at the limits of detection, if not simply a figment of the imagination. This preternatural quality is crucial because both science and the human intellect have evolved to handle the material world with relative ease. After all, when automobiles kill tens of thousands of Americans each year, the mechanism of our demise is relatively obvious, as it is with guns. Anxiety is not the issue. Caution is. If science manages to unambiguously identify the agent of an illness, as happened with the AIDS virus, the shadow of impending doom is dispelled by the light of knowledge, and the medical research establishment marches off to deal with it. The rest of us, or most of us, alter our behavior accordingly and the prophylactic industry flourishes. But we don’t, by and large, panic.

If no immediate cause of death or illness can be identified, or if no mechanism links the alleged agent of our woe directly to the illness or death-as was the case, for instance, with electromagnetism from power lines, silicone seeping from breast implants or, at least so far, genetically manipulated agricultural products-then fear sets in like ice on a pond, and an entirely different set of societal forces go to work.

This is where science fails us. The primary problem is that science is incapable of proving a negative. Over the years, researchers have looked at the effects of electromagnetic radiation at cell-phone-like frequencies on cells (the biological kind) in petri dishes and on lab animals and even humans, without coming up with any particularly believable evidence that cell phones themselves would be harmful. But here’s the catch: No matter how ingenious and copious the experiments, they could no more prove that cell phones do not cause cancer than they could prove the nonexistence of God. “It is scientific only to say what is more likely and what less likely,” as Richard Feynman put it, “and not to be proving all the time the possible and impossible.” When it comes to what is more or less likely, however, everyone has a different opinion on how to weigh the odds. That the scientific community and the lay public do so by different standards of evidence is made obvious by the common belief in phenomena-from UFOs, ESP and ghosts to the continuing incarnation of Elvis-that are not considered likely by most working scientists.

This proving-a-negative problem comes with an important corollary: Experimental science is also inherently incapable of achieving perfection. The experiment does not exist, nor will it ever, that can unambiguously throw up zeros across the board simply because the phenomenon it has set out to study is nonexistent. Rather, if done honestly, it will result in a range of values around zero, and the midpoint of this range is even likely to be above zero-a positive result, in the lingo-because it will reflect a host of subconscious factors that will push researchers to be slightly optimistic rather than rigorously detached. For those who want to believe that the phenomenon is real, the existence of these positive results, however close to zero, will constitute all the evidence they need.

This is simply a fact of human nature, one that Francis Bacon, the Abner Doubleday of experimental science, pointed out 400 years ago when he created the scientific method as a tool to overcome our inherently delusional thinking. “The human understanding still has this peculiar and perpetual fault of being more moved and excited by affirmatives than by negatives,” Bacon wrote, “whereas rightly and properly it ought to give equal weight to both; rather, in fact, in every truly constituted axiom, a negative instance has the greater weight.” Those of us who believe in ESP, for instance, do so because we have anecdotal evidence that it does exist, despite the decades of scientific experiments that suggest it does not.

As a result, little or nothing is needed in a scientific vein to initiate health scares, and even less to perpetuate them indefinitely. Indeed, they become inevitable and play themselves out with a certain relentless predictability. Their procession from meaningless beginnings to full-blown national anxiety could be dictated by a flowchart or programmed with simple software.

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