The tip-of-the-tongue (TOT) phenomenon refers to the experience of feeling confident that one knows an answer, yet is unable to produce the word. For example, in conversation or writing most people have had the occasional experience of trying, but failing to retrieve someone's name or a word from memory. This type of memory retrieval has been referred to as a tipof-the-tongue (TOT) state because one experiences the frustrating feeling that the retrieval of the word is imminent and on the "tip of the tongue." Although psychologists have long been aware of this phenomenon, Roger Brown and David McNeill (1966) conducted one of the first experimental studies of TOT states. In this study, they attempted to experimentally induce TOT states in college students by presenting definitions of relatively rare words (e.g., to give up the throne). The subjects' task was to name the word for the definition (e.g., abdicate). Brown and McNeill found that they could induce a TOT state on approximately 10 percent of trials.
Subsequent research on TOT states has been conducted by experimentally inducing TOT states in the laboratory or asking subjects to keep diaries of everyday occurrences of TOTs (Brown, 1991). These studies have yielded varied characteristics of TOT states. For example, TOTs are more likely to occur for infrequently used words. Interestingly, when experiencing a TOT state, subjects are often able to accurately retrieve information about the non-recalled word (e.g., the first letter of the word or the number of syllables). Thus, subjects seem to have partial information available about the target word, yet cannot retrieve the word. Also, subjects sometimes report an alternate word that comes to mind and seems to "block" the retrieval of the target word. These "blockers" often share semantic (i.e., meaning) or phonological (i.e., sound) features with the target word (e.g., abide for the word abdicate). Diary studies of naturally occurring TOTs have revealed that most often TOTs are resolved spontaneously, such that the target word seems to simply "pop into mind" after previous retrieval attempts have been abandoned (Burke, MacKay, Worthley, and Wade, 1991; Heine, Ober, and Shenaut, 1999).
There have been two competing theoretical explanations for why TOT states occur during memory retrieval. The blocking hypothesis states that TOTs are caused by an alternate, more accessible word that first comes to mind that then serves to block or inhibit the retrieval of the correct target word. Support for the blocking explanation comes from the experimental finding that presenting a phonologically related cue word with a definition for a target word resulted in more TOTs than when an unrelated cue word was presented (Jones, 1989; Jones and Langford, 1987). Similar results have been found by presenting cues that share orthography (letters) with the target word (Smith and Tindell, 1997). Also, it appears that TOTs are more difficult to resolve when an alternate word has come to mind than when there is no alternate word (Burke et al., 1991), possibly suggesting that the alternate word blocks the target word and thus causes the TOT.
On the other hand, the incomplete activation hypothesis states that "blocker" words are merely the consequence, not the cause of TOTs. According to this explanation, TOTs are caused by the weak or incomplete activation of the target word. Semantic information about the target word may be activated, but the corresponding phonological representation may be only partially activated. A more accessible, phonologically similar alternate word may become activated and at first appear to "block" the target word. Based on the incomplete activation hypothesis, one would expect that providing a phonologically related cue word with the definition should actually facilitate target retrieval, rather than produce a TOT state. Meyer and Bock (1992) provided initial evidence for the incomplete activation hypothesis. In three experiments that were designed to address these competing explanations (blocking versus incomplete activation), Meyer and Bock reported (1) semantically and phonologically related cue words facilitated rather than hindered target word retrieval (contrary to Jones's findings); (2) phonological cues facilitated retrieval more than semantic cues; and (3) these related cues facilitated retrieval even after an initial unsuccessful target retrieval attempt. Subsequent studies also have provided evidence that processing phonologically related words decreases TOT states and increases correct target responses (James and Burke, 2000), lending further support to the incomplete activation explanation of TOTs.
Although most people experience TOTs occasionally, there is evidence that TOTs may increase with age. TOT experiences represent a common memory complaint of older adults and thus have been extensively studied in the older adult population. Indeed, both laboratory and diary studies indicate that older adults report more TOT experiences and have less partial information available about target words than younger adults (Brown and Nix, 1996; Burke et al., 1991; Heine et al., 1999). The literature has been somewhat inconsistent regarding whether older adults report more or fewer alternate words (i.e., blockers) that come to mind while in a TOT state. There appears to be no age differences in terms of the percentage of TOTs resolved or the time to resolution. As might be expected, theoretical accounts for the increase in TOTs as a function of old age have focused on age-related deficits in word-retrieval due to (1) the interfering effects of related words that act as blockers that inhibit the retrieval of the target words; or (2) incomplete activation of the target due to degraded connections between the semantic representation and the phonological representation of the word (Burke et al., 1991; James and Burke, 2000).
There also has been an interest in the neural correlates of TOTs as a reflection of memory retrieval failure. Using neuroimaging techniques (event-related fMRI), Maril, Wagner, and Schacter (2001) scanned subjects while answering general knowledge questions. Subjects indicated whether they knew the answer (successful retrieval), did not know the answer (unsuccessful retrieval), or were in a TOT state. The results indicated that there was a selective response in anterior cingulate-prefrontal cortices of the brain during a TOT state, relative to successful and unsuccessful retrievals. This is interesting because this area of the brain has been associated with the control and resolution of cognitive conflict. Thus, these neuroimaging results seem to correspond with the behavioral experience of TOT states.
The experimental study of TOTs has provided psychologists with valuable information on the process of memory retrieval. Neuroimaging data may further delineate the neural underpinnings of this everyday memory phenomenon.
Brown, A. S. (1991). A review of the tip-of-the-tongue experience. Psychological Bulletin 109, 204-223.
Brown, A. S., and Nix, L. A. (1996). Age-related changes in the tipof-the-tongue experience. American Journal of Psychology 109, 79-91.
Brown, R., and McNeill, D. (1966). The "tip of the tongue" phenomenon. Journal of Verbal Learning and Verbal Behavior 5, 325-337.
Burke, D., MacKay, D. G., Worthley, J., and Wade, E. (1991). On the tip of the tongue: What causes word finding failures in young and older adults? Journal of Memory and Language 30, 542-579.
Heine, M. K., Ober, B. A., and Shenaut, G. K. (1999). Naturally occurring and experimentally induced tip-of-the-tongue experiences in three adult age groups. Psychology and Aging 14, 445-457.
James, L. E., and Burke, D. M. (2000). Phonological priming effects on word retrieval and tip-of-the-tongue experiences in young and older adults. Journal of Experimental Psychology: Learning, Memory, and Cognition 26, 1,378-1,391.
Jones, G. V. (1989). Back to Woodworth: Role of interlopers in the tip-of-the-tongue phenomenon. Memory & Cognition 17, 69-76.
Jones, G. V., and Langford, S. (1987). Phonological blocking in the tip of the tongue state. Cognition 26, 115-122.
Maril, A., Wagner, A. D., and Schacter, D. L. (2001). On the tip of the tongue: An event-related fMRI study of semantic retrieval failure and cognitive conflict. Neuron 31, 653-660.
Meyer, A. S., and Bock, K. (1992). The tip-of-the-tongue phenomenon: Blocking or partial activation. Memory & Cognition 20, 715-726.
Smith, S. M., and Tindell, D. R. (1997). Memory blocks in word fragment completion caused by involuntary retrieval of ortho-graphically related primes. Journal of Experimental Psychology: Learning, Memory, and Cognition 23, 355-370.