So, we’re heading into another pre-presidential campaign. And we all know what that means: Glowing speeches about “integrity.” Impassioned debate about the future of the nation. Photo ops of candidates pitching in to help out local communities.

And, of course, phantasmagorically nasty attack ads.

Now, every candidate decries “going negative,” and most voters claim they hate mudslinging. Normally, pundits and Joe Sixpack say what they want is “civility”; if a candidate expresses an opinion clearly and rationally, voters will listen to it and weigh it carefully. According to this “normative” model, voters read about the candidates’ positions, compare and contrast them, and pick the politician best suited to their interests. In this context, attack ads are just noise, unwanted distractions — a blight on the wholesome quest for civility.

But according to a pair of political scientists, attack ads are common because of one simple reason: They work.

After all, politicking is all about crazed emotion, not hard facts. That’s particularly true when it comes to TV ads — since TV is a medium far better suited to delivering heightened narrative and emotion than hard-facts data. So when it comes to political advertising, the scientists figured that the better way to analyze things is by using “behavioral decision theory”, which explains our choices by investigating our irrational, emotional urges. When the scientists looked at attack ads that way, they realized why going negative is so singularly effective. As a report on Allsci notes:

Unlike the normative model, which argues that all political advertisements are considered equally, prospect theory states that, say, voters are willing to take risks when they’re going to face a loss but otherwise, when they perceive only gains, they take as few risks as possible. This helps to explain when negative political advertising is used. Challengers against incumbents, prospect theory predicts, should use negative ads more often. According to Fox and Farmer’s research, this is true; challengers are more likely to use negative ads.

In case you didn’t recognize that picture above, it’s taken from the ad that forms the solid-gold standard of political crepuscularity: The infamous “Willie Horton” TV spot that the Republicans used to utterly demolish Michael Dukakis.

(Thanks to SciTech Daily for this one!)