In search of a Model Based on Lexical and Grammatical Complexities in Haliday's Systemic Functional Grammar: The Case Study of "Persian Language Reading for Non-Persian Learners"

The current study is to find the answer to these questions: (1) In complex texts، which one is more? Lexical complexity or grammatical complexity? (2) How is the interaction between vocabulary and grammar in producing the difficulty of the texts? (3) By using the results of this study، an educational model can be presented about the interaction between vocabulary and grammar in producing the complexity of the texts. For this purpose، 5 informative written texts which were extracted from 30 existent texts in the «Reading and Comprehension for advanced non-Persian Students» were selected (according to the rate of difficulty declared by Persian learners and instructors at Imam Khomeini international university). Then، the lingual complexity of those texts، in terms of vocabulary and grammar، was detected and extracted separately and statistically، based on the Haliday''s Systemic Functional Grammar (1985 & 2004). After that، to determine the way of interaction between the two factors (vocabulary and grammar) in producing the complexity، the most complex text was rewritten; once by using lexical tools and again by grammatical tools، so that they were changed into two more complex texts. Also، the two rewritten texts were given to the testees and they were asked about the level of the difficulty original text and the rewritten one. The results of the study shows that in creation of the original and natural texts، both lexical and grammatical tools، in minor variance، are used; though، in average، the complexity of written text is mostly of lexical type، rather than grammatical، and this is in accordance with the claim of the author of the book that believes the selected texts for teaching reading are original. The findings also illustrate that lingual complexity originated from vocabulary، with regard to the grammatical complexity، acts in an opposite way in producing the complexity of the text. In other words، increasing the lexical complexity، leads to the increase of text complexity، and grammatical complexity makes the text easier to understand. Finally، a basic model for the interaction between vocabulary and grammar in producing the difficulty of reading comprehension the written texts by advanced non-Persian learners، was introduced.