One of the tried and true tools in the anti-consumer activist’s arsenal is the food scare. Whenever a food-borne illness pops up, groups like the Center for Science in the Public Interest and People for the Ethical Treatment of Animals try to inflame public fear (except when that food scare happens to be spinach, of course). Their subsequent pronouncements usually fall some where between complete fabrications and irresponsible hype. But even with track records that should relegate them to the public opinion penalty box, activists are still successful at stoking food fears. Why? Last week’s TIME magazine cover story provides us with an answer.

Through interviews with notable biologists, psychologists, and professional risk analysts, TIME provides an explanation for the discrepancies between the real and perceived risk from certain health threats — notably the fear monger favorites of bird flu and trace levels of mercury in fish:

We agonize over avian flu, which to date has killed precisely no one in the U.S., but have to be cajoled into getting vaccinated for the common flu, which contributes to the deaths of 36,000 Americans each year … [According to John Graham, the former administrator of the federal Office of Information and Regulatory Affairs] pollutants in fish can be dangerous, but for most people-with the possible exception of small children and women of childbearing age-the cardiac benefits of fish easily outweigh the risks.

The basic reason for this cognitive disconnect is the way the human mind is organized. As the experts told TIME, we disproportionately fear “catastrophic risks … Unfamiliar threats are similarly scarier than familiar ones … [We] misjudge risk if we feel we have some control over it …”

These traits give us a natural tendency to commit what University of Chicago Professor of Law Cass Sunstein calls “probability neglect.” Sunstein believes we fixate on some threats (like foodborne illness) and inflate their actual prevalence, which is normally pretty low.

As private risk consultant Dan McGinn puts it, “We used to measure contaminants down to the parts per million. Now it’s parts per billion.”