If you turned on the radio anytime in the last week, you're likely to have heard the sounds of the King of Pop.

Michael Jackson's music has been all over the place in the wake of his death. KyXy, the soft-rock station devoted to soccer moms, went all-Michael, and even rock station KPRi got into the act, managing to find a cover of the Jackson Five's "I Want You Back" by singer KT Tunstall.

But there's a funny thing about Michael Jackson on the radio: He wasn't heard a whole lot before now, at least over the past several years. In fact, his music was mainly relegated to two types of music stations -- those that play oldies (like 105.7 The Walrus) and the ones devoted to soul and R&B music (Magic 92.5).

"He wasn't given much thought by the 'mainstream' stations because he just kinda fell off the radar," said Dave Mason, morning host at The Walrus.

"He was definitely a spotty presence on radio for somebody who'd had so many hits," agreed Sean Ross, an executive editor at radio-info.com.

In fact, many music stations have whittled their playlists of huge 1980s artists such as John Mellencamp, Bryan Adams and Bruce Springsteen to three or four songs each, Ross said.

How come Jackson almost disappeared? It has a lot to do with research. Radio stations pay people to ask listeners what they think about songs so they can create playlists that make the most people happy. If a song doesn't score well with focus groups, it won't be played much.

Darrel Goodin, general manager at KSON and its sister stations, speculated that Jackson's songs lost some of their appeal because the artist himself did. It was most likely because of his legal problems, at least in part, Goodin said.

"I'm not saying that's right, but most likely the reason. I am guessing that the sad truth is that the outpouring of passion for his music after his death was not as evident prior. Given the magnitude of his influence, and the number of records that he sold, there can be no other explanation."

Radio may not have understood Jackson's popularity before, but it certainly does now.

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If you're a conservative, you're more likely to listen to Rush Limbaugh than turn to National Public Radio. And if you're liberal, you're probably don't spend your time tuned to Roger Hedgecock, Sean Hannity and Rick Roberts.

Pretty obvious, right? Yes, but now researchers have gone and confirmed what we think we know: People like to hear opinions that back up what they already think. In a study published this week in a journal called Psychological Bulletin, researchers say we do indeed turn to sources of information that confirm our biases, especially when it comes to things like politics and religion.

"Never having any contact with the other side is a very safe way of protecting your beliefs. It's a little bit primitive, but successful," said study co-author Dolores Albarracin, professor of psychology at the University of Illinois at Urbana-Champaign.

Peter Ditto, a professor of psychology at UC Irvine, said there's a bit more to it. We listen to, say, a conservative host because we believe he -- or in rare cases, she -- looks at the world through the correct prism.

"Republicans turn to Fox News not because they think it will confirm their beliefs, but because they believe they are the unbiased keepers of the truth -- and that MSNBC and CNN are biased toward the left," Ditto said. "Liberals do exactly the opposite."

There's a funny thing about this study: It mentions people who are biased toward conservative points of view, such as Dick Cheney, who supposedly demanded that Fox News be on the television whenever he entered a hotel room.

But there's little or nothing about people who are biased toward liberal perspectives. Michael Young, an associate professor of psychology at Southern Illinois University Carbondale, noticed this discrepancy.

"It is always easier for us to identify these biases that suggest closed-mindedness in others than it is to identify them in ourselves or those who agree with us, even if you are a scientist who studies bias," he said.

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There was sad news last week about the death of the local disc jockey known as Gary Cocker. According to sdradio.net, he was 59 and died of pancreatic cancer.

Cocker, whose real name was Helmut Kerling, worked at a number of stations, including KGB, KFMB-AM, KCBQ, Sets 102.1 (now KPRi) and K-Best. Local radio types flooded sdradio.net with tributes.

"He was not afraid to tell a program director (a station boss) he thought he was an idiot," wrote Sonny West, morning host at KyXy. "This was Gary's downfall at a few stations, but smart PDs, secure in their manhood, listened to Gary's ideas and concepts and often put them into practice. And that made for a better radio station."

Randy Dotinga is right about everything, so opposite opinions are simply unnecessary. E-mail him at NCTimesRadio@aol.com.