We’ve All Experienced This Um, Um, Uh . . .

Babbling along mid-sentence, you are suddenly struck silent, throttled by a dumbfounding inability to come up with the next word. The thing appears lost somewhere in the gray space between your ears.

This is it, you think. My brain has outlived its warranty.

But the aggravating phenomenon is quite common--common enough to have a name: tip-of-the-tongue experience, or TOT. It is the inability to retrieve a word from memory, twinned with an uncanny sense of knowing that you know the word.

Studies suggest that the brain retrieves words through a system of networks that process thoughts into speech; the TOT occurs when a snag blocks the word from making it to the articulation stage.

“It has to do with not being able to remember what the word sounds like,” said Deborah M. Burke, a psychology professor at Pomona College, who has researched the TOT phenomenon and aging. “A word is retrieved by remembering its sound. People are twice as likely to find the word if something they read or hear during a TOT shares some of the missing word’s sounds.”

People in the throes of a TOT almost universally describe a “feeling of knowing.” The word’s first and last letter are often ferreted out along with “alternate words” that have an equal number of syllables and the same syntactic and grammatical value. For instance, a 75-year-old woman staring at her blender in an angst-ridden word search sputtered “vibrator.” A college student trying to think of the word “Winnebago” struggled until she blurted: “rutabaga.”

“Alternate words suggest that we can get some of the sounds but not all of them,” Burke says.

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Studies suggest that the early stages of mental deterioration may impact the process of retrieving word sounds more strongly, and that conceptual information about a word is retrieved independently of its sound. Alzheimer’s disease, Parkinson’s disease, strokes and aphasia weaken connections that control retrieval of word sounds more than those responsible for retrieval of meaning.

While TOTs do become more frequent with age, even children sometimes get stuck. The rate can vary widely, but studies show that younger adults (18-22) experience TOTs about once or twice a week, while older adults (65-75) have twice that number. Some TOTs come to mind in a few seconds; others can take days.

Advanced brain-imaging technology used by Willem Levelt, director of the Max Planck Institute for Psycholinguistics in the Netherlands, provides some of the most riveting evidence that TOTs are like verbal traffic jams in the brain. Levelt and other researchers say that the harder you try to retrieve a word, the more elusive it becomes.

“The typical effect here is, you may not be able to solve it and then you stop and it just pops up in the mind,” he says. “No one knows what causes the word to come to you. The best advice is let it go and it will come automatically.”

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“Pop up” is a term people use to describe sudden retrieval after surrendering the search, also a mystery to researchers. Does the unconscious keep searching? Is there an environmental trigger or is there a little man rooting around the neural pathways in search of the word, as some study subjects report imagining?

There is no definitive answer, but some linguists speculate that the “incubation effect” might be at work, the same process by which mathematicians solve problems. You ponder, struggle, pull out clumps of hair, then clear your mind of the problem and voila! The answer sails through somehow.

Burke thinks pop-ups are serendipitous. “We think that there is a chance occurrence in life that makes the word pop up. Like, someone who’s trying to think of ‘Ojai’ might say ‘Oh, hell.’ The thing people need to realize is that retrieval is just a normal part of cognition . . . not necessarily proof your brain is falling apart.”