The great economic historian Robert Fogel, who died last year at the age of 86, wrote in a 2005 paper that he was surprised by the resilience of scholarly attention to the secular-stagnation theory. He found that the term began to be used in 1938, during a time of world economic despair, and that its currency grew rapidly, hitting a peak in the 1940s. Lively debate on the topic endured in the 1980s, he noted, though the discussion eventually decayed to almost nothing by the 1990s.

There is little talk about secular stagnation in scholarly circles today. The recent chatter has centered in the news media, in conference panel discussions and in the blogosphere.

We can contrast this secular stagnation story with the narrative that drove down the stock market in 2011. By May 10 of that year, the Standard & Poor’s 500-stock index had already doubled since its financial-crisis bottom on March 9, 2009. And then the index fell by about 20 percent from May 2 to Aug. 9.

What set off that decline? It had to do with a different thought virus: the worry that Congress wouldn’t raise the debt ceiling in time to prevent the United States from defaulting on its debt. The nation didn’t default, but on Aug. 5, 2011, S.&P. downgraded the national debt for the first time.

While reports on this drama were alarming, it’s not obvious why they should have caused such a sharp market decline. Clearly, consumer confidence fell. And for both individual and institutional investors, my own crash confidence index, based on questionnaire surveys conducted by the Yale School of Management, dropped almost as far as its record low at the worst of the financial crisis in 2009. People worried that stock prices would fall. The “expected” component of the Michigan Consumer Sentiment Index dropped lower than at the worst of the financial crisis in 2009.

Why was the default story so virulent? The Michigan Consumer Sentiment Report for July 29, 2011, said that although respondents might not have understood the issues surrounding the national debt, they were hearing “repeated warnings of ‘dire economic consequences,’ ” and because of their experiences were “keenly aware of the grave consequences of excessive personal debt.” And there was much talk that a first federal default would have been an epic humiliation — or so it was being depicted at the time.

But that narrative ended when Congress raised the debt ceiling. The stock market soared again, once the news stopped reinforcing that fear of dire consequences.

The current secular-stagnation story is less dramatic than that of the debt crisis. But because it’s so vague, the negative feedback loop can’t be resolved as neatly. The question may be whether this thought virus mutates into a more psychologically powerful version, one with enough narrative force to create a major bear market.