Lexical Diversity Measures’ Review And Classification

Abstract

This paper reviews various lexical diversity (LD) measures and their classification. The authors define the most significant advantages and disadvantages of the measures and investigate the main scopes of LD application. They include measuring LD in the speech of children and people with aphasia, checking progress in learning a foreign language, and investigating different writing styles of certain authors. Results show that the most frequently used measure is the type-token ratio (TTR), which means the ratio of different words (types) to the total number of words (tokens). The most important problem of TTR and other measures based on TTR is that the more tokens a text has, the less is the TTR value. This has led to the development of other measures; some of them are based on a TTR formula, thus, they do not solve the problem and the calculation result is also affected by the text length. In that case, the texts with different length cannot be compared. Another group of measures rests upon the TTR formula supplemented by a principle of sample forming. These measures solve the problem of the TTR partially or completely, though they often require some extra instruments. Fortunately, these instruments are available on the Internet and demand no particular knowledge on their working principle or in programming. Contemporary researchers tend to use independent measures, because texts mostly have different length and the dependent measures cannot give proper results.