A gap is a space between two objects or a break in continuity. A research gap is a break or missing part of the existing research when you define the research gap or the problem space you are defining what is known and what is missing in the existing research. The "problem space" of a study is a definition of the topic, the problem statements or research gaps mentioned by other researchers, and the steps other researchers took to answer the research question. The problem space is a way to identify and establish boundaries for your research, it helps to guide what should be included or excluded from your research. The problem statement expresses how your study will answer or fill the research gap.
The problem space is thus comprised of identifying what is known about a topic, understanding how it has come to be known (the theories, designs, methods, instruments), and then figuring out what is not yet known (or perspective not explored). Problem spaces are built by taking note of the limitations and recommendations discussed in the empirical research articles you gather as you build your literature review.
When looking to find discussions of research that has yet to be done (AKA research gap) in existing articles there are a few keywords to look out for such as limitations identified, further research needed, needs clarification, not been reported (studied, reported, or elucidated), suggestions for further research, questions remains, poorly understood, and/or lack of studies
Below are two examples of types of passages to look for.
Example of a Limitations Section
From the article:
Spanhove, V., De Wandele, I., Kjær, B. H., Malfait, F., Vanderstukken, F., & Cools, A. (2020). The effect of five isometric exercises on glenohumeral translations in healthy subjects and patients with the hypermobility type of the ehlers-danlos syndrome (heds) or hypermobility spectrum disorder (hsd) with multidirectional shoulder instability: an observational study. Physiotherapy, 107, 11–18. https://doi.org/10.1016/j.physio.2019.06.010
From this passage, an argument could be made for performing a similar study, but with 3D analysis.
Example of a Recommendation for Further Research
Some articles will go beyond discussing their limitations and describe further research that should be done.
For example, this article:
Carey, J., Pathak, A., & Johnson, S. C. (2020). Use, Perceptions, and Awareness of LibGuides among Undergraduate and Graduate Health Professions Students. Evidence Based Library and Information Practice, 15(3), 157-172. https://doi.org/10.18438/eblip29653
Suggests several different avenues of further research:
Review articles can help formulate a gap, or at least point out a direction to look for one. Since they provide an overview of the published literature, they can give you a head start on what kinds of research are lacking.
How to Locate Review Articles: Systematic Reviews, Literature Reviews, and Meta-Analyses
Seo, H.-J., Sohng, K.-Y., Chang, S. O., Chaung, S. K., Won, J. S., & Choi, M.-J. (2019). Interventions to improve hand hygiene compliance in emergency departments: a systematic review. The Journal of Hospital Infection, 102(4), 394–406. https://doi.org/10.1016/j.jhin.2019.03.013
Pursuing a health care topic? Search Cochrane Reviews or Joanna Biggs EBP as well as the more general databases.
Example of a Review Article
Review articles can clarify where a lack of research exists. To then establish the problem space fully, you will need to track down the articles cited in the review.
For instance, consider the following passage from this review article:
Martin, A. (2019). An acquired or heritable connective tissue disorder? A review of hypermobile Ehlers Danlos Syndrome. European Journal of Medical Genetics, 62(7), 103672. https://doi.org/10.1016/j.ejmg.2019.103672
This is indicating a need for longitudinal studies for this condition to better understand the relationship between muscle strength and muscle waste. Further examining the cited articles would establish this avenue for a study.