Being consistent is important when preparing your manuscript. For example, you don’t want to flip flop between ml and mL or Fig. and Figure. Once you disrupt your reader’s flow with inconsistent wording and formatting, it’s hard to get their attention back. In general, it’s best to pick one format and stick with it.
However, there is one major exception to this “rule”. Verb tenses. They can, and should, change throughout the manuscript, depending on the section or on what is being described.
In the Abstract, a summary of the experiments performed, their results, and overall conclusions are presented. In most life science manuscripts, this information is presented in the past tense. In the physical sciences, the present tense is sometimes used. If you mention subsequent experiments that you’ve planned, you would use the future tense.
The Introduction is the section where facts and information obtained from previous studies are presented, and the present tense is used most. However, sometimes the past tense is appropriate; you might say that a certain group of authors showed a certain thing to be true. For example, “X et al. showed (past tense) that DNase I cleaves (present tense) DNA.” In this case, the past tense is used to indicate that the study was carried out prior to the present time, and the present tense is used to show that what they found is, and continues to be, true.
In the Materials and Methods section, the past tense is often used because the experiments were carried out prior to the preparation of the manuscript (hopefully!). In some fields, like engineering, the present tense may be used.
The Results section describes what was found in the study. Typically, the results are written using the past tense because the findings were made in the past. However, when referring to figures and tables, the present tense must be used because the figure/table is visible in the present and can be viewed by the reader. For example, “Figure 5 shows (present tense) the change in mRNA expression over time”, but “The expression of GSK1 decreased (past tense) over time.”
In the Discussion, the results are analyzed and compared with those from previous studies. Most of this section should be written in the past tense. The present tense may be used when presenting a well-known fact or information that is generally accepted by the research community. In addition, when comparing your results with those from other, related studies, the present tense should be used. For example, you might write, “The expression levels of the Y mRNA that we found agree (present) with the results of Z et al.” There may also be use of the future tense if discussion about how the experiments could be improved is included in this section or if future experiments are outlined.
If the manuscript has a Conclusion, this will usually be written in the past tense because it is essentially a summary of your findings. If additional, if future work is mentioned, it should be presented in the future tense. For example, “We will isolate (future) the other proteins in the complex.”
These are the basic guidelines to verb tenses in your manuscript. Please also note that there are some variations between fields and between journals. Happy experimenting, and happy writing! May your next manuscript be a success!
(Please retain the reference in reprint: http://www.letpub.com/index.php?page=author_education_verb_tenses)