08 June 2009 by Ewen Callaway
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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'."
It's a…, it's a…
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.
Rarity Is Key
As with previous experiments, monolinguals had fewer tip-of-the-tongue experiences than bilinguals, about 7 words versus 12, out of a total of 52 – though Pyers' team counted only instances where the volunteer knew the word.
However, Spanish bilinguals experienced roughly the same number of tip-of-the-tongues as sign language bilinguals. This rules out the possibility that similar-sounding words compete for our brain's attention in tip-of-the-tongue experiences.
More likely, tip-of-the-tongue experiences occur when we're trying to recall rarely used words, Pyers says.
"People often have tip of the tongue experiences for proper names, again because we don't use them very frequently," she adds.
Seconds later during an interview with New Scientist, Pyers struggled briefly to recall the name of a colleague. "I can picture this guy in my head," she said.
Brief Exposure
It may be relatively easy to generate these moments in the lab or in conversation, but another common mental quirk, déjà vu, has been much harder to recreate and study, says Alan Brown, a psychologist at Southern Methodist University in Dallas, Texas, who studies both phenomena.
"The fascinating thing about déjà vu is that it is so complex and amorphous," he says. "How do we unpack that and try to push that experience in sort of more circumscribed ways in the lab."
See our feature: Déjà vu: Where fact meets fantasy
One of several theories to explain déjà vu suggests that these moments are triggered by a conscious recognition of a visual cue that we processed subconsciously moments before.
Teaser Image
To trigger this effect in the laboratory, Brown showed volunteers a cryptic pattern on a computer screen followed by an unfamiliar symbol and then the question: "Have you ever encountered this symbol prior to the study?"
On some occasions, the same symbol had appeared for 35 milliseconds behind the cryptic pattern – too briefly to be consciously observed. On others, this "teaser" symbol was different from the one that would follow and, in some trials, no teaser appeared.
"What we wanted to do was make something where you could attribute a familiar experience to something prior to the study … not just a minute or two ago, but a day or two months," Brown says.
After going through 144 such tests each, two dozen university students said they had seen the symbol before the experiment 22 per cent of the time when an identical teaser had preceded the symbol. With a different teaser or none at all, volunteers said they had previously seen less than a tenth of the symbols.
Uncommon Experience
Moreover, in a post-experiment debriefing, 80 per cent of volunteers said they were confused about whether they had seen a symbol before, and half said they had a déjà vu experience in the lab. Most volunteers claimed they normally experience déjà vu twice a year or less.
"We really weren't expecting someone to have that 'whoa' experience, because we're not recreating all the pieces," Brown says.
Genuine déjà vu experiences often incorporate sound and emotions. In hopes of creating – and manipulating – more realistic episodes in the laboratory, Brown plans next to use virtual reality to create an even more immersive environment.
Journal reference: Pyers et al., Cognition (DOI: 10.1016/j.cognition.2009.04.007)
Journal reference: Brown et al., Psychological Science (DOI: 10.1111/j.1467-
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