Given the impossibility of withholding language from children to assess sensitive period effects on syntactic acquisition, the study of second language learning has been seen as an alternate method that can be used to understand the natural time course of language acquisition. In order to do so, both the age at which immersion is begun and the differences between the first and second languages being observed must be taken into account. The studies described herein assess age and language differences in second language acquisition to find specific areas of syntax which may pose difficulties, and to account for disagreements between those who argue that second language acquisition is affected by age and those who argue that second language fluency is likely at any age. Age seven is described here as the end of the optimal sensitive period, with those who begin learning English after that age facing reduced end state performance under certain circumstances. For instance, under some conditions second language fluency is likely, and under others it is not. The circumstances affecting the acquisition of second language syntax will be described through three types of transfer possible between the first and second language: "positive transfer," "negative transfer," and "null transfer," with the case of "null transfer" providing the greatest difficulty for later second language learners. When "positive transfer" and "negative transfer" are possible, a second language learner who begins learning after age seven may still be able to perform nearly as well as a native speaker. [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/en-US/products/dissertations/individuals.shtml.]