Nonetheless, there are certain ways to predict what the public will be interested in, he noted, regardless of whether the topic is politics, foreign affairs, disasters, science or anything else. “Polarizing social issues involving family, sexuality, patriotism and God engender the highest levels of attention,” Robison wrote. In addition, proximity to home can make a big difference, as can human interest. When Jessica McClure fell down a well in Texas in 1987, one year after the Chernobyl disaster, sixty-nine percent of America paid rapt attention to her rescue. “That reading put Baby Jessica in eighth place among all 1,300 stories” [the Pew studied examined], Robison wrote. “Chernobyl, in contrast, failed to rank in the top 100 stories.”

Thankfully, celebrity scandal ranks lowest among all news preferences. Writing for The Nation, Eric Alterman argues that the lack of interest in this subject is the study’s “most shocking” conclusion. The finding is especially surprising given the “major changes in the news ‘menu,’” that Robison describes, where “substantial coverage” devoted to stories such as Paris Hilton’s incarceration and Anna Nicole Smith’s death.

Yet what is truly fascinating is the explanation for this contradiction between interest and coverage: “Even the smallest shifts in ratings can cause news organizations to alter substantially their news focus,” Robinson writes, and often toward “a lower common denominator.” But these alterations, marked by “saturation” coverage, are often temporary and aimed at capturing the niche rather than the national audience. This harkens back to the earlier, chicken-and-egg discussion of where interest lags behind coverage, and where it exceeds coverage. “That the national news audience does not shift its news diet nearly so quickly as news organizations shift their news menu” is one of the most important take-away messages for journalists in Robinson’s study.

Robinson implies that on a national scale changes in coverage tend to mold public interest rather than vice versa. If so, journalists must be especially cognizant of their influence on not only opinions about the news, but also on what is considered newsworthy to begin with. Responsible editors and reporters like to think they do not pander to people’s basest interests, but rather guide and educate them. So perhaps the more pressing question is not, how have preferences changed, but rather to what degree and how quickly does content influence those preferences? Does a diet of more junk food create an appetite for more junk? Does a healthy diet create the reverse?

And if an outlet such as CNN chooses to even temporarily woo a niche audience for the sake of ratings - by chasing the Anna Nicole Smith story, for example - what is sacrificed with regard to the national audience? Hopefully, reports such as the Robinson’s study will help guide journalists as they try to find answers.

Curtis Brainard is the editor of The Observatory, CJR's online critique of science and environment reporting. Follow him on Twitter @cbrainard.