Coh-Metrix Measures

Abstract

As we have discussed in the previous chapters, Coh-Metrix was developed to analyze texts on multiple characteristics and levels of language and discourse. Although the original inspiration for the development of Coh-Metrix was to provide automated metrics of text cohesion (hence Coh -Metrix), it became clear very early in the Coh-Metrix project that there was a need in the research community for a more comprehensive tool capable of analyzing texts at multiple language and discourse levels. The Coh-Metrix team has collected and evaluated hundreds of indices since the beginning of the project. The indices scale texts on characteristics related to words, sentences, and connections between sentences. The measures that have been included in Coh-Metrix naturally align with theories of discourse, which assume that comprehension operates at multiple levels (e.g., Graesser & McNamara, 2011; Kintsch, 1998; Snow, 2002). These theoretical frameworks describe representations, structures, and processes at multiple levels of language and discourse. As described in Graesser and McNamara (2011), five levels have been proposed most commonly in these frameworks: (1) words , (2) syntax , (3) the explicit textbase , (4) the situation model , and (5) the discourse genre and rhetorical structure (i.e., the type of discourse and its composition). The theoretical alignment of Coh-Metrix with these levels is described in previous chapters. The number and particular measures provided by Coh-Metrix depend on the version and the type of tool. We have developed public versions of the tool that analyze individual texts and have provided between 40 and 80 theoretically grounded and validated indices. We have also developed internal versions of Coh-Metrix that analyze texts in batches and that include 600–1,000 indices, many of which are redundant and many of which have not been validated (and thus we do not release them to the public). Although the specific Coh-Metrix measures vary somewhat across versions and tools, the banks of measures are quite similar. This chapter describes the indices that are provided in Coh-Metrix 3.0. In this chapter we describe all of those indices in the order they are output in the tool, except those that are associated with readability and text ease, which are described in Chapter 5. The indices that are described in this chapter and Chapter 5 are listed in Appendix A. Comparative norms for each of the indices are provided in Appendix B by grade level for three texts genres (language arts, social studies, and science).