Life screws with people: neglectful parents, inconsiderate spouses and partners, selfish children, boorish bosses, and disdainful co-workers create scores and scores of attention-deprived people desperately seeking approval. Most frequent manifestation of this subconscious desire is excessive, out-of-place talking - lengthy stories with self-boosting subtext.
This type of behavior is usually classified as social awkwardness. I don't know a single person capable of keeping a grip on himself under any circumstances. Once in a while certain conditions come together and something activates the stupid switch even in the most brilliant people. I've seen some pretty impressive humans falling into this mode during lectures, important meetings, fundrasing parties, and social gatherings.
During 2010 New York's World Science Fair, I attended a panel Consciousness: Explored and Explained with the screenwriter Charlie Kaufman (Being John Malkovich, Eternal Sunshine of the Spotless Mind, Adaptation) and the neuroscientist Giulio Tononi. It was monitored by the actor and director Alan Alda (better known as Hawkeye Pierce of M*A*S*H) - a fairly smart guy who got close to popular science by hosting PBS's Scientific American Frontiers. One concept that Giulio Tononi has described was too much for Mr. Alda to grasp. He restated the scientist's words once, was corrected, then again, and again. Finally, he realized that he wasn't getting it, but he couldn't help himself - he kept talking, and talking, and talking...
Hey, sometimes I catch myself doing it and thinking, "What's going on? Why am I relating my interpretation of A Streetcar Named Desire to this uninterested person?" But only very self-aware people are capable to recognize the symptoms and stop themselves.
Consequently, the degree of this affliction widely varies. In some people it gets triggered by a selected audience (sometimes even one particular individual), or specific circumstances. I had a sort of a paralyzing effect on my boss of two years ago. He would be acting his aloof self around everybody else, but every time he would come to my office, he ended up ranting. Eventually, I became wary of starting even super-important discussions with him. It was always, "Let me tell you,.." and we would be off on an absolutely irrelevant tangent. At one point he was telling me that he shares a surfing coach in East Hampton with Gwenyth Paltrow and Chris Martin. I kept thinking to myself, "I am not impressed, dammit!"
In many people this trait blows up to extreme proportions: people simply cannot stop themselves. They don't need any special circumstances or triggers - they grab every chance they get to talk, even if they have nothing to say. In public these people are usually extroverted, talking non-stop. The overwhelming popularity of Facebook and Twitter is the testimony to the pandemic proportions of verbal diarrhea.
In social situations you can simply walk away, or turn your phone off to stop seeing three tweets per minute. However, you cannot do the same at work. You have to deal with it one way or another. Ok, so not everyone can find the right way to tell their bosses to shut up. And my advice - don't do it. Even if it seems that you've done it in the mildest way possible, they never forget it. And, as we all know, no one can hold the grudge as long as bosses do. On the other hand, when it comes to your peers or subordinates, the issue must be addressed if it interferes (and it does) with the normal course of a meeting, an assignment, or a working day.
The best way to approach it is with a friendly private talk. Most likely the person is not aware that what he is doing is an obvious display of insecurity, and that people recognize it as such. Explain to the person that he achieves the exactly opposite results: while trying to impress and seeking approval, he gets co-workers and supervisors annoyed. To earn this person's trust, you can share your own experience in similar situations (just like I did here). Most importantly, tell them that the best way to make a difference and get appreciated is by doing the best job they can.