As you begin to gather the literature, you will want to critically read for what has, and has not, been learned from the research. Use the Discussion and Future Research sections of the articles to understand what the researchers have found and where they point out future or additional research areas.
See this example below from Frisch, C. & Huppenbauer, M. (2014). New insights into ethical leadership: A qualitative investigation of the experiences of executive ethical leaders. Journal of Business Ethics, 123(1), 23-43. DOI: 10.1007/s10551-013-1797-9
Continue to ask critical questions of your topic – who, what, when, where and how – about the population or setting, conditions or variables, methods or analysis, and measurement or outcomes. Also consider what has not been explored in the study and what may be a possible ‘gap’ or opening for your potential research and contribution to the topic. Use organizational tools such as charts or Venn diagrams to map out the research you find from scholarly articles. These methods may be helpful to organize what information you have found and what is shared among the literature, as well as to identify what areas may be missing in the research. This page provides a matrix for organizing research from multiple articles.
For additional examples, try a Roadrunner Search using this search string: ("Literature review") AND (gap*)
These three examples below illustrate how researchers from different disciplines (psychology, business, and education) identified gaps in existing literature: