Why Your Brain Just Can't Remember That Word

June 8, 2009— -- Most of the time the brain works as it ought to: limbs move, memories are retrieved and experiences processed. But occasionally things go awry.

In tip-of-the-tongue experiences, for instance, words suddenly and perplexingly go missing only to reappear seconds or minutes later. Another brain quirk – déjà vu – confirms the fallibility of memory. Now two new studies have shed light on both phenomena.

Nearly everyone has tip-of-the-tongue moments, but bilinguals seem especially prone to these momentary lapses in vocabulary, says Jennie Pyers, a psychologist at Wellesley College in Massachusetts.

One possible explanation is that similar-sounding words compete for our brain's attention. Since bilinguals know twice as many words as monolinguals, there's more chance for tip-of-the-tongue experiences.

"Often when we're having tip-of-the-tongue experiences, words that sound the same come to mind," Pyers says. "There's a sense that you do know the first letter; there's a sense that you might know how many syllables it is."

Alternatively, they could occur when our brains recall rarely used words, Pyers says. "It's much easier to retrieve a word like 'knife' than 'guillotine'."

Since bilinguals, by definition, speak two languages, they are bound to use many individual words less frequently than monolinguals.

In hopes of narrowing down these explanations, Pyers' team compared 11 Spanish-English bilinguals with 22 people who used English and American sign language (ASL). Since the signers' second "tongue" makes no use of sound, there is no opportunity for sound-alike words to elicit tip-of-the-tongue experiences, says Pyers, who is fluent in ASL.

To provoke tip-of-the-tongue moments, the researchers showed the bilinguals, as well as a control group of 22 English monolinguals, pictures of dozens of different objects and challenged the volunteers to name them in 30 seconds. The viewed objects – which included axes, weathervanes, gyroscopes, nooses and metronomes – were obscure enough to elicit tip-of-the-tongue experiences in all but one participant.