From American Scientist:
Our ability to use words is a critical part of our species’ mastery of language. In practice, that mastery comes down to saying what we mean without having to think too much about it. When we have something to say, we first retrieve the correct words from memory, then execute the steps for producing the word. When these cognitive processes don’t mesh smoothly, conversation stops. Suppose you meet someone at a party. A coworker walks up, you turn to introduce your new acquaintance and suddenly you can’t remember your colleague’s name! My hunch is that almost all readers are nodding their heads, remembering a time that a similar event happened to them. These experiences are called tip-of-the-tongue (or TOT) states. A TOT state is a word-finding problem, a temporary and often frustrating inability to retrieve a known word at a given moment. TOT states are universal, occurring in many languages and at all ages.
People resolve TOT states using a variety of methods. Some are conscious strategies, such as mentally going through the alphabet to find the word or consulting a book or person. However, the most common method for resolving TOT states is an indirect approach: relaxing and directing one’s attention elsewhere. The missing word suddenly comes to mind without thinking about it. These “aha!” moments are known as “pop-ups.” The purpose of this article is to explore the cognitive processes that cause pop-up resolutions and to document changes in these processes with healthy aging. The ability to resolve TOT states changes significantly in old age, which is particularly important because older adults have more TOT states than do younger adults.