Slips of the tongue? Mixed up consonants? Verbal blunders are more than simple mistakes to linguist and journalist Michael Erard. The author of Um... Slips, Stumbles, and Verbal Blunders, and What They Mean, Michael explores what gaffes in speech tell us about language, and ourselves. We called him to learn, um, more about this subject:

VT: How did you become fascinated by verbal slips and blunders?

Michael: I wanted to tell stories about language, and one important story of my life has been how language feels different when I write it and when I speak it. In 1999 and 2000, when George W. Bush was running for president, I was attracted to the story of how he used language, not only for what he said but for how we heard it. The way he used language was getting a lot of attention.

VT: In what way?

Michael: Not so much for the way that he put his sentences together but for the way that he made mistakes. They were real mistakes, real malapropisms, like saying "Grecian" instead of "Greek" or the one that everyone loves, "misunderestimate." These slips became evidence for some people in the media that Bush was not a normal speaker -- and maybe because he wasn't a normal speaker he wasn't intelligent, and maybe we had to question his character.

At the time I knew that I wasn't going to vote for Bush but I thought, well, I make slips of the tongue, too, and I say "uh" and "um" a certain amount. I wanted to know, is that normal? What does it mean to be a normal speaker? So I started looking into it and found a lot of scientific research. And I also started to encounter people in different professions who treated these verbal slips differently than most people, who commonly think that "uh's" and "um's" are meaningless and slips are just funny. If you talk to interrogators and detectives, for example, they'll tell you that they use interruptions and pauses in speaking as indications of whether someone is telling the truth or whether someone's feeling anxious.

VT: Because if you're lying you use more of them?

Michael: There's some disagreement about whether you can tell whether someone is lying by how self-interrupting they are when they speak. There's some evidence that shows that it's not the lying that causes these slips, but the fact that people are in an unfamiliar situation. If they're in an interrogation room, for instance, they might be nervous - but maybe that's because they are actually innocent and afraid of getting pegged as guilty.

When you make stereotypical assumptions about interrupted, spontaneous speaking you can actually miss some things. People who are very skilled liars sometimes speak very smoothly. So how can you catch them if you are only paying attention to the way someone speaks?

VT: Interesting.

Michael: Slips of the tongue, though, are particularly useful for linguists and psychologists, who have used them as evidence of how language operates in the brain. This study has been going on for about 40 years and has been incredibly fruitful.

VT: Let's step back for a moment. How do you and other experts in the field define a "blunder"?

Michael: In my book I talk about blunders in two ways. First, it's slips of the tongue -- accidents of speaking. For example, last weekend I tried to say "beef jerky" and it almost came out as "jeef berky." I stopped myself before I said the full phrase. I had planned to say "beef jerky" but instead my brain swapped the consonants. And my wife was recently putting away groceries, and I casually asked what we were having for dinner. "Turkey bars," she told me. "Turkey bars?" I asked. Turns out that as she was answering, she was putting a box of fudge bars into the freezer.

The other category is what is called "disfluencies," that is, people saying "uh" and "um," restarting their sentence, repeating words, saying a fragment of a word, things like that. Slips of the tongue happen on average about once or twice every thousand words; however, we typically notice one about once a week. Hopefully my book will make people notice them more frequently.

VT: Once every thousand words?

Michael: Which is much less often than the disfluencies, which occur about once every 4.4 seconds. When we're speaking spontaneously, about 5% to 8% of the words that we say are somehow disfluent or include disfluencies.

VT: That's quite a bit!

Michael: There are more disfluencies than there are slips of the tongue. Of all disfluencies, "uh" and "um" occur in the greatest number.

VT: From your research, what do all these speaking errors tell us about how we humans think about and process language?

Michael: It tells a lot. For one thing, we don't communicate in whole sentences. We communicate in phrases or in clauses. In spontaneous, conversational language we put phrases together and those phrases are typically pretty short.

It also tells us that there's a lot of variation in what each of us does individually. Each of us has an individual style, a sort of verbal finger print. Adults will be more likely to make a slip like "cuff of coffee" than "cup of coppee" because they have more practice with the sounds of the language. Some people say "uh" or "um" more. Other folks restart their sentences more. It depends whether you're a careful, planning sort of person or whether you just hurtle forward and have full confidence that you can always go back and change what you say if it doesn't come out right. Me, I'm an "ummer."

VT: What about "Freudian slips" -- are they real?

Michael: We think of "Freudian slips" now as a slip of the tongue that has an obvious innuendo or some sort of obvious sexual or obscene connection. But to Freud, all the slips that we make -- off color or not -- have the same cause, which is an emotional cause. It's an unconscious desire that I'm repressing that automatically comes out. So Freud would say that when I made my "jeef berky" slip, there was some emotional meaning to that.

VT: Do you agree with him?

Michael: Freud couldn't explain those sorts of mundane slips. But he did give us a really great way of listening to people very closely and using clues -- very minor and otherwise insignificant clues -- to reach conclusions about who people are and what they want. At the same time he probably also set back the scientific study of slips of the tongue for quite a while because he connected slips more to an individual speaker, not the act of speaking in general.