Editor's note: Todd Rogers is a social psychologist and assistant professor of public policy at Harvard's Kennedy School of Government. Michael I. Norton is an associate professor of marketing at the Harvard Business School and co-author of the forthcoming book "Happy Money: The Science of Smarter Spending."
(CNN) -- The emerging consensus about Thursday night's vice presidential debate is that there was a high degree of professionalism on the stage. Why? Martha Raddatz kept the candidates on point -- and on time.
Contrast her command with what we saw from Jim Lehrer in the first presidential debate. It did not take an expert in debate analysis to observe that the candidates seemed to wrest control of the debate from the moderator at times. Raddatz, on the other hand, frequently interrupted the candidates when they spoke too long. She asked pointed, specific questions, and often repeated them for good measure.
Perhaps most important, she often (though not always) pushed the candidates to answer direct questions when they were being evasive.
When politicians dodge questions, they send an implicit signal that they believe that their answer to the actual question could negatively affect how voters view them. These are exactly the questions we need them to answer.
In an ideal world, we could count on moderators to probe each time a candidate dodges a question. But let's consider their job. Moderators are news personalities who have professional reputations and network audiences they need to maintain; their professional success depends on their being liked and respected.
In televised debates, moderators must wrangle two of the most powerful men in the world whose goal is to assert, bloviate and evade. This is a hard job. In fact, Lehrer wrote in a recent book that he would not moderate again after having moderated 11 presidential debates. (Despite that desire, he was coaxed by the Commission on Presidential Debates into moderating a 12th this year.)
There are real risks as moderators push back when politicians dodge direct questions. A case study occurred on the show "Newsnight." Jeremy Paxman asked the same question of UK politician Michael Howard 12 consecutive times, repeating the question verbatim after each evasive answer. In the end, his question was never answered, and both of the men's reputations suffered in the eyes of some viewers: Howard was seen as evasive and untrustworthy, but Paxman was viewed as pugnacious and aggressive.
In the first presidential debate on October 3, both President Obama and Mitt Romney -- like all politicians -- attempted to dodge questions. On several occasions, for example, Romney was asked a specific question but offered an answer to an entirely different (though seemingly related) question. When asked "Do you support the voucher system (for Medicare)?" he replied, "What I support is no change for current retirees and near-retirees to Medicare. And the president supports taking $716 billion out of that program."
Notice the dodge? Romney offered an answer to a question about whether he was going to change Medicare for current retirees, not whether he supported a voucher system for Medicare in the future.
Why do politicians get away with dodging questions? Viewers often simply fail to notice. Our research has found that by default, viewers' limited attention is first directed toward assessing whether they like the candidates, not toward evaluating whether the answer offered is directly related to the question asked.
In a typical study from our research, one group of viewers watches a debate in which a politician is asked a question ("What will you do about health care?") to which he offers a direct answer ("I'm glad you asked me that. We need universal health care because..."). They are later asked to recall what question he was asked and are very likely to recall that he was asked about health care.
A different group of viewers, though, watches a debate in which a politician is asked a different question ("What will you do about illegal drug use?") to which he provides the same answer he offered when he was asked about health care. When asked later, these viewers struggled to recall what question the candidate was asked, often thinking he was actually asked about health care, mistaking the topic of his answer for the topic of the question.
But all hope is not lost for stopping would-be dodgers. Our research (PDF) also documents a simple, inexpensive strategy to help viewers detect when politicians dodge questions, taking at least one of the million tasks that moderators are asked to perform off of their plate. We have found that posting the text of the question on the screen while politicians answer can enable viewers to detect even the most artful dodges. In fact, CNN has made this practice their official policy.
When Candy Crowley moderates Tuesday's presidential debate, we hope all of the networks broadcasting the event will help her the way we should help all moderators, from Lehrer to Raddatz and beyond: Let's post the questions on the screen.
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The opinions expressed in this commentary are solely those of the authors.