The Present Perfect in the Rhetorical Divisions of Biology and Biochemistry Journal Articles.

Most English for science and technology (EST) teachers will agree with Walker (1967) that for the nonnative speaker of English, the present perfect is one of the most difficult tenses in the English verb system. Sometimes it is confused with a present tense and at other times a past. The most difficult task for the teacher is to teach students when to use it. This difficulty is further intensified when normative speakers are required to read and write scientific discourse and are confronted with the rhetoric of scientific English. The purpose of this study was to investigate the use of the present perfect in each rhetorical division (Introduction, Methods, Results and Discussion) of biology and biochemistry journal articles to determine whether the meanings conveyed by the perfect are related to the rhetorical functions of each division. Although the main focus was the examination of the relationship between rhetorical function and the use of the present perfect in the four rhetorical divisions, other issues such as the choice between the use of either the present perfect or the past tense to report past research, and time and frequency indicators occurring with the perfect, were examined and are discussed herein. EST researchers have demonstrated a relationship between rhetorical function and grammatical choice in technical English and have pointed out the inadequacy of using a sentence-oriented approach to grammar which describes grammatical choices only in syntactic and semantic terms (Lackstrom, Selinker & Trimble, 1970). They have also shown that factors other than time-tense relationships such as paragraph organization, core idea, or degree of generality expressed at various points in the paragraph may govern the choice of tense (Lackstrom, Selinker & Trimble 1970; Selinker, Trimble & Vroman, 1972). Lackstrom et al. (1970) reported that the present tense occurred where technical English rhetoric required the expression of a generalization. However, Oster (1981) found that the present perfect rather than the present tense was used to express a generalization about past literature and that the use of the present perfect implied to the reader that the topic discussed within that sentence would be elaborated in subsequent discourse. Lackstrom, Selinker, and Trimble (1973) have made a distinction between the use of the past tense and the present perfect by scientific writers to express the rhetorical function of reporting past research. In a study of verb forms in the rhetorical sections of MS theses in biology, chemistry and physics,