Positive, interesting, and truthful statements can effectively support an argument that filling a GAP in understanding is necessary to advance scientific understanding.

To justify the time and effort necessary for research, scientists must propose to study a problem that many people would agree is important.  Once scientists have identified an important research problem, the objective of scientific research is  typically to make discoveries and generate new understanding (although replicating experiments is a valuable and under-represented effort; Nosek, 2015).  Identifying "Gaps" in our understanding is important for making discoveries  (Weissberg & Buker 1990; Lingard, 2018).

DEFINITION: A "gap" in understanding is some aspect of the world (or universe) that we do NOT understand well enough, but we DO have enough information around the "gap" to create reasonable hypotheses. We can think of the "gap" as being between our current understanding and a more complete understanding that is important to achieve.

A "gap" in understanding is usually presents us with a question, and it is often helpful to express a "gap" as an answerable question.

There are many types of "gaps" in our understanding; many types of questions that are important to ask. We might seek to understand how a type of protein contributes to cell function, or how vaping affects brain development in teens, or why our knees bend forward instead of backward. In each case, we currently have some understanding of each process (the functions of other proteins, other disruptors of brain development, knees that bend forwards and backwards in other animals) that can help us ask, and answer, our question.

Identifying gaps in understanding involves surveying the published literature, and using published findings to construct deductive or inductive arguments to support the existence of a reasonable gap. Most often, scientists have informally identified a gap in understanding before writing the Introduction section of a paper. Therefore, making arguments for a gap in understanding can use the strategy of reverse engineering: using the proposed gap in understanding to determine what information readers need in order to understand the proposed gap. 

For example, consider the gap in understanding: "We do not know if interleaving academic training with motor skills training results in more learning than blocked training for either academics or motor skills."

The gap statement suggests that the Introduction would need to define and/or review:

A) What "interleaving" practice is.

B) What "learning" is, and how learning can be measured.

C) Why specific types of academic study and motor skills are most relevant to investigate.

D) Current knowledge of the effects of interleaving on academic study relative to blocked study.

E) Current knowledge of the effects of interleaving on motor skills relative to blocked study.

F) In addition, the Introduction may choose to review other relevant evidence, such as the plausibility that interleaving academic and motor training increases learning for both relative to blocked training (e.g. by investigating the neural mechanisms of learning). 

However, the Introduction must do much more than simply define terms and describe current knowledge!

An effective Introduction identifies concepts, reviews research, and defines terms in the context of an ARGUMENT that filling the gap in understanding is necessary to advance scientific understanding. 

Making an argument that an experiment is necessary to advance scientific understanding is not easy. Creating a reasoned outline can help us to construct our overall argument that filling the identified the gap in understanding is necessary to advance scientific understanding. A reasoned outline can be built from the conclusions of reasoned sub-arguments.  Once a strong overall outline has been created, specific references to previous research can be used as premises to support the sub-conclusions of the outline. Both the outline and the full text of the paper will benefit from using clear logical transitions. Moreover, the challenging process of creating strong arguments typically requires many revisions.

Three principles are useful for constructing arguments to defend an important gap in understanding:

1) Write positively. Construct arguments from information that is known, where premises can be directly supported.

2) Write in a compelling way. Use interesting logical transitions:  the conjunction "but" and disjunction "or."

3) Write truthfully, using statements of appropriate scope.

1) Write positively.

DEFINITION: "Positive" indicates that the information is known (not unknown). Positive information comes from conclusive (sound or strong) research findings.

To identify and defend a "gap" in understanding, many writers are tempted to directly argue that there is a absence of scientific understanding in a particular area. For example, writers may make statements like "There are few studies that have investigated X..." Arguments about the absence of understanding may be strong when made after a comprehensive review or meta-analysis of the scientific literature by a highly-experienced expert in a field. However, most writers have not reviewed ALL of the scientific literature in an area, and do not typically have recognized expertise in a field. Therefore, arguments for the absence of understanding or information are NOT likely to be strong.

Instead, students (and scientists who are not writing comprehensive reviews) must make arguments based on what is KNOWN, NOT what is unknown. 

One strategy for identifying a gap in knowledge is to use a dichotomy:

A) Identify two important areas of inquiry that are related, but different in defined aspects. 

B) For each area, construct positive, reasoned arguments to support a conclusion that represents the current state of understanding of the area.

C) Identify aspects where the two conclusions do not overlap, or potentially even conflict, as GAPS in understanding.

A final argument that one gap in understanding is particularly important to fill constitutes a useful transition to the hypotheses of the study. 

Therefore, even though gaps in understanding represent areas where more research is necessary, arguments to support gaps can (and should) be constructed from premises based on existing data. Positive arguments can provide strong evidence for gaps in understanding.

When possible, use repetition and consistent frameworks to simplify the presentation of the Introduction. For example, arguments can be organized around a framework such as:

* Introduce a concept and define necessary terminology.

* Present evidence supporting to the concept in the form of an inductive or deductive argument.

* Make a reasonable conclusion from the evidence.

APPLICATION: Base arguments on information that you have, not on speculation about the absence of information.

2) Write in a compelling way

Identifying a gap in understanding involves contrast or disjunction. However, Introductions need not be limited to a single contrast or disjunction! Conflict and opposition are interesting for readers, and potentially encourage understanding and learning.

Constructing positive arguments often involves reviewing research findings that are consistent with each other or with more general hypotheses. However, "laundry lists" of research findings connected with "and" logical transitions may not be the most engaging arguments for the Introduction (even if the arguments are logically sound or strong). Therefore, it is helpful to not only review evidence consistent with overall findings, but to also identify and discuss areas of conflict.

Of course, the most important aspect of presenting research is that the research faithfully represents current understanding. Compelling and interesting writing are desirable, but are only appropriate when the arguments are valid representations of current understanding.

APPLICATION: Use contrasts and disjunctions to faithfully represent current understanding in an engaging way.

3) Write truthfully, using statements of appropriate scope.

Arguments in the Introduction should faithfully represent the current state of understanding. Two important requirements for faithfully representing current understanding are:

A) Selecting research that reasonably represents the current understanding of a research area. 

Often, more research has been conducted in an area than can be included in the Introduction of a paper. Therefore, selecting relevant research findings is necessary. Selected research findings should be an un-biased (or balanced) representation of current understanding.

B) Using statements of appropriate scope.

Authors must be careful to avoid inaccurate or overly-general statements about research findings. For example, generalities about "all" or "most" research findings are seldom justified. Authors should select appropriate modifiers and helping verbs to ensure that statements have the scope justified by the data.

APPLICATION: Revise writing to make sure that evidence justifies the scope of premises and conclusions.

Using positive arguments to strongly argue for a GAP in understanding leads naturally to the primary objective of scientific research: to develop and test hypotheses that can help fill the gap in understanding.

The amount of information necessary to identify a gap in understanding differs for each study. However, typically 3-5 paragraphs are sufficient to construct positive arguments and identify reasonable gaps.

The second section of the Introduction presents arguments that there is a GAP in understanding in an important topic. Positive arguments can use existing information to identify gaps in understanding.