Corpus linguistics identifies the qualitative difference in the characteristics of spoken discourse vs. written academic discourse. Whereas spoken discourse makes greater use of finite dependent clauses functioning as constituents in other clauses, written academic discourse incorporates noun phrase constituents and complex phrases. This claim can be extended to the contrast between academic written texts and more informal oral-like written texts. This study examined whether this qualitative difference in syntactic structures affects second language learners' syntactic parsing in a written academic text. For the purpose of this research, a think-aloud protocol of reading a typical written academic text was carried out with 31 undergraduate students at a U.S. university who demonstrated near-passing scores and above on the Japanese language proficiency test level 2. The statistical analysis, using Kendall's tau, revealed that advanced proficiency in terms of oral-like written texts does not guarantee the ability to parse syntactic structures in written academic texts.