The Type-Token Ratio and Vocabulary Performance

The Type-Token Ratio (TTR), a measure of lexical diversity, was correlated with four measures of vocabulary performance: the Peabody Picture Vocabulary Test-Revised, the Oral and Picture subtests of the Test of Language Development, and the Test of Written Language. The vocabulary tests were administered to 21 6-, 7-, and 8-yr.-old children from whom language samples were obtained for the application of three Type Token Ratio measures: the TTR-Total for the whole language sample, the TTR-100 for language samples of 100 words, and the CTTR, a procedure intended to be independent of language sample size. One correlation of .45 (between the CTTR and the Oral-TOLD) was significant. More research on validity is necessary to clarify the measurement domain of the TTR, if it is to be useful clinically.