Lexical Richness Revisited: Blueprint for a More Economical Measure*
Noam Ordan, Victoria Itskovich, Miriam Shlesinger, Ido Kanter · Journal of Quantitative Linguistics · 2010
According to Heaps' Law, the increase in the number of types, S, in natural texts consists of L tokens and follows a power law, S = K · L β, where K and β are constants. After presenting the theoretical background, we try to predict the behaviour of Heaps' Law asymptotically using a 25-million-token corpus of original English. We then examine this law in a corpus for English, where original English corpora (O) are compared with three subcorpora of translations into English (T) from three different languages. We show that (1) K and β change along the L-axis: as K grows, β gets smaller; (2) K is larger in the translations and β larger in originals; (3) for a given L, S of O is higher than that of S of T. Finally, we show a more economical way to tell O from T, based on increase in types belonging to specific parts of speech. Last, we discuss the consequences of this research for information retrieval and for translation studies.