selecting the right word from the “mental lexicon” (a mental dictionary of the speaker's vocabulary)
retrieving its sound pattern (called its “form”)
executing the movements of the speech organs for articulating it.
Word-finding difficulties can potentially arise at each of these stages of processing.
When a healthy speaker can't retrieve a word from their lexicon despite the feeling of knowing it, this is called a “tip-of-the-tongue” phenomenon by language scientists.
Often, the frustrated speaker will try to give a bit of information about their intended word's meaning, “you know, that thing you hit a nail with”, or its spelling, “it starts with an H!”.
Tip-of-the-tongue states are relatively common and are a type of speech error that occurs primarily during retrieval of the sound pattern of a word (step three above).
What can affect word finding?
Word-finding difficulties occur at all ages but they do happen more often as we get older. In older adults, they can cause frustration and anxiety about the possibility of developing dementia. But they're not always a cause for concern.
One way researchers investigate word-finding difficulties is to ask people to keep a diary to record how often and in what context they occur. Diary studies have shown that some word types, such as names of people and places, concrete nouns (things, such as “dog” or “building”) and abstract nouns (concepts, such as “beauty” or “truth”), are more likely to result in tip-of-the-tongue states compared with verbs and adjectives.
Less frequently used words are also more likely to result in tip-of-the-tongue states. It's thought this is because they have weaker connections between their meanings and their sound patterns than more frequently used words.
Laboratory studies have also shown tip-of-the-tongue states are more likely to occur under socially stressful conditions when speakers are told they are being evaluated, regardless of their age. Many people report having experienced tip-of-the-tongue problems during job interviews.
When could it spell more serious issues?
More frequent failures with a broader range of words, names and numbers are likely to indicate more serious issues.
When this happens, language scientists use the terms “anomia” or “anomic aphasia” to describe the condition, which can be associated with brain damage due to stroke, tumours, head injury or dementia such as Alzheimer's disease.
Recently, the actor Bruce Willis's family revealed he has been diagnosed with a degenerative disorder known as primary progressive aphasia, for which one of the earliest symptoms is word-finding difficulties rather than memory loss.
Primary progressive aphasia is typically associated with frontotemporal or Alzheimer's dementias, although it can be associated with other pathologies.
Anomic aphasia can arise due to problems occurring at different stages of speech production. An assessment by a clinical neuropsychologist or speech pathologist can help clarify which processing stage is affected and how serious the problem might be.
For example, if a person is unable to name a picture of a common object such as a hammer, a clinical neuropsychologist or speech pathologist will ask them to describe what the object is used for (the individual might then say “it's something you hit things with” or “it's a tool”).
If they can't, they will be asked to gesture or mime how it's used. They might also be provided with a cue or prompt, such as the first letter (h) or syllable (ham).
Most people with anomic aphasia benefit greatly from being prompted, indicating they are mostly experiencing problems with later stages of retrieving word forms and motor aspects of speech.
But if they're unable to describe or mime the object's use, and cueing does not help, this is likely to indicate an actual loss of word knowledge or meaning. This is typically a sign of a more serious issue such as primary progressive aphasia.
Imaging studies in healthy adults and people with anomic aphasia have shown different areas of the brain are responsible for their word-finding difficulties.
In healthy adults, occasional failures to name a picture of a common object are linked with changes in activity in brain regions that control motor aspects of speech, suggesting a spontaneous problem with articulation rather than a loss of word knowledge.
In anomia due to primary progressive aphasia, brain regions that process word meanings show a loss of nerve cells and connections or atrophy.
Although anomic aphasia is common after strokes to the left hemisphere of the brain, the associated word-finding difficulties do not appear to be distinguishable by specific areas.
There are treatments available for anomic aphasia. These will often involve speech pathologists training the individual on naming tasks using different kinds of cues or prompts to help retrieve words. The cues can be various meaningful features of objects and ideas, or sound features of words, or a combination of both. Smart tablet and phone apps also show promise when used to complement therapy with home-based practice.
The type of cue used for treatment is determined by the nature of the person's impairment. Successful treatment is associated with changes in activity in brain regions known to support speech production. Unfortunately, there is no effective treatment for primary progressive aphasia, although some studies have suggested speech therapy can produce temporary benefits.
If you're concerned about your word-finding difficulties or those of a loved one, you can consult your GP for a referral to a clinical neuropsychologist or a speech pathologist.