The transfer of speech features to writing is a common problem in the writing development of non-native speakers of English because students often do not recognize when this transfer is occurring and how it can impact a piece of discourse. The purpose of this study is to investigate how the factors of proficiency, extraversion, and use of English influence this transfer in non-native speakers of English who are learning English for academic purposes. Proficiency was determined by the English as a second language writing course in which participants were enrolled at the time of the data collection. Participants also completed a measure of their level of extraversion and a questionnaire measuring the extent to which they use English, and submitted two pieces of writing, a descriptive essay and a process essay. The extent to which writing samples showed evidence of speech features was measured using a technique based on the concept that groups of cooccurring linguistic features in a text cause it to resemble speech rather than isolated features alone.