It is a familiar story.  Experts warn that the sky is falling.  The public seems to ignore their alarms.  The experts despair.

Two new pieces of survey research arrived last week, each designed to throw some light on the complex interplay between expert knowledge and public opinion. Mainly, they succeed in illuminating the limits of survey research.

In the first study, five members of the Department of Zoology at Cambridge University decided to try to bring some measurement to bear on a current controversy -- to gauge whether the Hollywood eco-thriller "The Day After Tomorrow" does more harm than good.  They reported their findings last week in an earnest letter to Science.

The zoologists noted the growing consensus among scientists about the seriousness of global warming. But the instant ice age that, in the movie, follows a sudden shutdown of the North Atlantic Conveyer (the warming ocean current whose presence keeps northern European winters relatively mild) is considered to be, to put it mildly, an exceptionally unlikely event.

When the team tested levels of concern and knowledge of 200 adults, either on the way into or out of four theaters in southern England, they found that the story clearly heightened movie-goers' environmental concern, measured by the share of a hypothetical £1000 they chose to allocate to the mitigation of climate change, as opposed to four other good causes.

Unfortunately, the film also seemed to undermine their understanding of what to expect next.   Using a pop quiz -- which of these six possible effects have been predicted for the United Kingdom by 2100? -- the zoologists found those who saw the flick often walked out with less realistic expectations than the gradual rise in temperature that is predicted by mainstream science.  Not a few expected the Thames to begin freezing over.

Thus the power of a 125-minute feature film to raise public concern was very great, concluded the zoologists.  If only slowly rising sea levels, warmer winters, drier summers and widespread extinctions could be made to seem equally dramatic. Then we might actually begin taking the steps -- emissions caps and trading, higher petroleum taxes -- necessary to contain the problem.

The second survey, a much more elaborate study by Alan Blinder and Alan Krueger of Princeton University, poses the twin questions, "What Does the Public Know about Economic Policy, and How Does It Know It?"

The Princeton economists devised a complicated questionnaire to elicit information about how citizens formed their views about taxes, the federal budget deficit, the minimum wage, Social Security and health insurance.  It took fifteen to seventeen minutes to administer over the phone; was given to 1002 respondents who were asked to describe themselves as being liberal, conservative, moderate or non-political; and produced a welter of cross-tabulations and regression analyses -- enough to take up 60 pages of the current Brookings Papers on Economic Activity.

When they were done analyzing their standardized little conversations, Blinder and Krueger found that ideology played a stronger role in shaping public opinion about economics than either self-interest or knowledge about how the economy works (which they defined as being more or less what they themselves believed to be the case).

From this they concluded that economists' narrow view of human beings as being well-informed, pragmatic and extremely self-interested was almost certainly mistaken. Ideology seemed to serve as a rule-of-thumb for deciding what position to take when real knowledge, or at least information, was lacking.

Blinder and Krueger were left with a puzzle, however. Those surveyed regularly spoke against their own interests. (Whether they were actually prepared to act was, of course, another question). Therefore they seemed to be either unusually confused about where their own self-interest lay, or else habitually generous,  putting what they perceive to be the common good ahead of their own narrow self-interest.

The questions seems likely to be put to a test, since three of the five topics in which the economists were interested are said to be on the verge of crisis -- the federal budget deficit, the Social Security program and the health insurance system.  

Survey research is in its infancy.  Tying to extract something memorable from these studies, I found myself wishing for a really good case study of what happens when the relevant decision-makers decide that the peril is real -- and act.

One such example would be the story of the rapid adoption of the Montreal Protocol on Substances that Deplete the Ozone Layer, signed in 1987 and toughened in 1990 and 1992.  Through it, governments around the world agreed to phase out the production and consumption of various commercial substances, chiefly chlorofluorocarbons, that were destroying a layer of ozone in the stratosphere which protects the planet from harmful ultraviolet radiation. The measures appear to be working.

Better yet, the story of Reagan deficits deserves a careful telling. Created in the early 1980s by massive tax cuts, a potentially disastrous widening gyre  was stabilized in 1982 by a behind-the-scenes technical measure, and the resulting chronic imbalance finally redressed in the 1990s through the complex interaction of various organs of public opinion and the political leadership of George H.W. Bush, H. Ross Perot, Bill Clinton and Newt Gingrich.

The current Bush administration has acted on one interpretation of that story. Vice President Dick Cheney told journalist Bob Woodward in his book Plan of Attack that "Reagan proved deficits don't matter."

Would anybody out there, besides the Bushies, care to bet?