Source: after James and Burke

You're at a restaurant with a friend, and he's just finished describing a movie he really enjoyed. "That reminds me," you say, "you just have to see, um...." Some of us have these frustrating tip-of-the-tongue (TOT) experiences all too often, and a new study published in the November issue of the Journal of Experimental Psychology: Learning, Memory and Cognition suggests they stem from the brain's inability to make strong enough connections among the various sound parts needed to form a sought-after word. "There are two levels in getting a word," explains Pomona College psychologist Deborah M. Burke, one of the authors of the study. "First, you have to select the specific word you want, and then you have to get the sound code for that word from memory. In a TOT experience, we're saying that people have the idea, the conceptual or semantic information about a word--and even know they've got a word to express it--but they just can't retrieve the sounds."

The notion that TOTs occur because of weak connections among stored sounds is known as the transmission deficit (TD) model. Burke and her husband, psychologist Don MacKay, proposed the model in 1991 as an alternative to the widely accepted inhibition, or "blocking," hypothesis, which suggests that TOTs occur because words that sound like an intended word block its retrieval. To test the TD model, Burke and her current collaborator, Lori E. James of the University of California at Los Angeles, designed two experiments in which they asked 108 people to answer a variety of general-knowledge questions; the answers were target words known to provoke a high rate of TOTs. The participants responded with the answer, "TOT" or "Don't Know."

In the first experiment, participants had to pronounce a list of 10 words before seeing the question (see illustration). Sometimes the list contained words that had nothing in common with the target word. Other times, however, the list contained five "priming words"--words that were phonologically related to the target word. As expected, when participants pronounced words sharing sounds with the target word, they made more correct responses and had fewer TOT experiences than when they pronounced words that had no phonological relation to the target word.

In the second experiment, participants answered the question without any list. Only if they entered a "Don't Know" response or experienced a TOT state were they then given a list. Again, the researchers found that in cases where the participants had initially answered TOT, their probability of resolving the word increased 25 to 50 percent if they were then primed with phonologically similar words. These findings refute the blocking hypothesis, the authors argue, which would have predicted exactly the opposite results.