The purpose of this body of work was to gain a clearer understanding of the potential cognitive factors that may contribute to Specific Language Impairment (SLI). This study attempted to simulate a performance profile of SLI in typically developing children within a grammaticality judgment task, featuring structures historically difficult (third person singular -S and auxiliary BE) and easy (plural -S and progressive -ING) for individuals with SLI. Cognitive load was manipulated through the length of the sentences to be judged, and individual differences in phonological short term memory (PSTM) and working memory were measured (WM). For a successful simulation to occur, problematic structures should display lower performance than easier structures, particularly for longer sentences, even after taking into consideration individual differences in cognitive abilities. A successful simulation was not achieved as lengthening failed to polarize performance between the historically easier structures and historically difficult structures in the systematic way predicted, even after accounting for differences in working memory ability. [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.]