A universal problem to our society is the dramatic increase in the number of security threats, risks, and vulnerabilities to our nation's computer systems, data, and infrastructure. Our future success depends upon the problem-solving and thinking abilities of professionals entering the Information Assurance and Security (IAS) field. These professionals will be faced with many problems that are complex, ill-defined, and multi-disciplinary in nature. But how do we, as educators, prepare these professionals to be successful? Are traditional approaches sufficient for the complexity they will face? This study examines ways of increasing learners' expertise of ill-defined concepts through the use of varying types of representations. Of particular interest is to what extent the number and context of representations increase learners' conceptual understanding of an ill-defined concept. Research suggests that the more varying the context of the representation presented to the learner the greater the understanding. Through a quasi-experimental research methodology, students were assigned into one of three groups and given multiple representations of an ill-defined concept "threat analysis". After each treatment, students created concept maps of their understanding of threat analysis, which was then scored against an expert concept map. Results show that multiple representations did increase conceptual understanding of an ill-defined concept from the first treatment to the second with diminishing returns thereafter. The varying contexts of the representations was not a factor, however the use of different instructional strategies did show a difference over the three treatments. Future research in examining how the structuredness of the representations presented to the learner increases conceptual understanding of ill-defined concepts will be of benefit to the field. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]