Size and Complexity There are simply too many words to teach and learn one at a time. Estimates of adult vocabulary size range from about 40,000 (Lorge & Chall, 1963) to 156,000 words (Seashore & Eckerson 1940), and it has been claimed that elementary school children acquire from eight (Nagy and Herman 1987) to more than 14 (Miller 1977) words per day.
Not only are there many words to acquire, there are also subtle and complex properties of words that competent users have acquired. Quite often, the meaning of a word is not nearly adequately represented by a synonym. As Finegan (1999) points out, words that appear to have the same meaning refer to slightly different concepts or are used in slightly different ways (e.g. the difference between vagrant and homeless.)
Also, when we acquire a word we acquire considerable knowledge about its grammatical properties. English speakers, for example, can freely add un to many adjectives, e.g. producing unhappy from happy, and but cannot do the same with sad. Professional grammarians have struggled to properly describe the generalizations underlying such phenomena, and they are rarely taught. Vocabulary teaching methods typically focus on teaching simple synonyms, and thus give only part of the meaning of the word, and none of its social meanings or grammatical properties.
Competence without Instruction People with large vocabularies and good writing ability do not generally claim to have developed them through study. Smith and Supanich (1984) tested 456 company presidents and reported that they had significantly larger vocabulary scores than a comparison group of adults did. When asked if they had made an effort to increase their vocabulary since leaving school, 54.5 percent said they had. When asked what they did to increase their vocabulary, however, about half of the 54.5 percent mentioned reading. Only 14 percent of those who tried to increase their vocabulary (3 percent of the total group) mentioned the use of vocabulary books.
Light Reading and Vocabulary Growth Research by Hayes and Ahrens (1988) suggests that lighter reading can play an important role in helping readers move to more demanding texts. According to their findings, it is highly unlikely that much educated vocabulary comes from conversation or television.
Hayes and Ahrens found that the frequency of less-common words in ordinary conversation, whether adult-to-child or adult-to-adult, was much lower than in even the lightest reading. About 95% of the words used in conversation and television are from the most frequent 5000.