Uni-edit English Writing Tip: Present Perfect Tense and Past Tense in
your Introduction

Difficulty: Advanced

How many times have you been told the following: “the past tense denotes
an event that happened in the past, while the present perfect tense
denotes an event that happened in the past, which has present
consequences.”? But, what about the Introduction section of research
papers? Aren’t all of the past findings relevant to my present research?

Confused? So are we! Here is an easy guide.

Present perfect Present perfect is often used for broad statements about
trends in the field. Temporal adjectives like “recently” and “long
considered” and words like “gather attention” and “draw criticism” often
suggest the present perfect tense. This is because these events did not
occur at specific point in time: rather, they are trends.

Correct: The contribution of agricultural production to greenhouse gas
has long been debated. Correct: Recently, the idea that some crops leave
larger CO footprints than others has gathered 2

attention. Correct: Some researchers have argued that crops that require
heavy use of nitrogenous fertilizers, such as potatoes, leave a larger
CO footprint than crops that require less, such as legumes. 2

This usage of present perfect includes cases where the date—a specific
point in time—is expressed in parentheses: because the date is not a
grammatical part of the sentence.

Correct: Some researchers have argued that crops that require heavy use
of nitrogenous fertilizers, such as potatoes, leave a larger CO
footprint than crops that require less, such as legumes (2002). 2

Simple past When the date of a study is expressed in the body of the
sentence, past tense is necessary. In fact, present perfect sounds
unnatural.

Correct: Smith et al. conducted a 2-year field experiment in 2009 and
2010 in rice paddies to learn about the connection between rice
production and greenhouse gases emissions.

In the Introduction Section, past tense usually applies when the
specific authors are referenced by name.

Correct: Smith et al. conducted a 2-year field experiment in rice
paddies to learn about the connection between rice production and
greenhouse gas emissions. Correct: Bouwmann et al. (2002) argued that
crops that require heavy use of nitrogenous fertilizers, such as
potatoes, leave a larger CO2 footprint than crops that require less,
such as legumes. Explanation: Notice that when “Bouwmann et al.” was
“Some researchers” in the Present perfect explanation above, it was
present perfect. This is because “some researchers” is not specific,
whereas “Bouwmann et al.” is specific.

The same principles apply to you: “we” or “the authors of the present
study” are specific researchers, so past tense should be used to report
findings of your past studies.

Correct: We previously conducted an experiment to learn about the carbon
footprints for various crops grown in Taoyuan County (2011).

Negative sentences The present perfect is more common when the
grammatical tense is negative (i.e. when “not” is used.) This is
especially true with verbs like “investigated”, “determined”,
“revealed”, etc.

Correct: Whether reducing potato crops is a viable strategy to reduce
greenhouse gas emissions has not yet been determined.

Consider that if something has never been investigated, there is no
specific time when it was not investigated: compare “A polar bear was
born in the zoo yesterday” with “A black polar bear has never been
found”.

That being said, again, the simple past is more appropriate if the
specific date or authors are written in the sentence.

Correct: Smith et al. conducted a 2-year field experiment in rice
paddies to learn about the connection between rice production and
greenhouse gas emissions. However, they did not consider the effects of
nitrogenous fertilizers.

END OF TIP