Academic research articles often involve the frequent use of lengthy noun phrase structures, and those seeking to write such texts, both native and non-native alike, would need to become familiar with this characteristic feature of the register. Biber, Gray and Poonpon (2011) have hypothesized a series of stages predicting development in writing complexity through the increased use of complex phrasal constructions. The purpose of this study is to compare abstracts by MA-level L1 Persian writers, PhD-level L1 Persian writers, and published writers from the field of applied linguistics in terms of phrasal modification features. Our findings revealed that the MA group differed significantly from the expert writers in the use of four types of modifiers: pre-modifying nouns; -ed participles as post-modifiers; adjective-noun sequences as pre-modifiers; and multiple prepositional phrases as noun post-modifiers. The PhD group however did not show any significant difference in producing noun modifiers when compared to expert writers except for multiple prepositional phrases as noun post-modifiers. The findings of this study help further our understanding of how academic writing becomes more complex with experience.

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