The grammatical role of subject is characterized with definiteness (thus has high referentiality), animacy, agency, and stability. By contrast, object, usually indefinite and inanimate, is affected by the verb in some way and thus changed in its state. These characteristics of the grammatical roles of subject and object offer us a sound explanation for the general tendency of word order in a simple declarative sentence. Given that subject is more referential and more stable than object, while the human cognitive system favors beginning an utterance or a sentence with a linguistic unit of high referentiality, so the natural candidate for the first position should be subject, which is followed by the verb and object that tends to bear new information. This gives rise to the dominant word order in natural languages: SVO. Such a word order conforms to Communicative Dynamism (CD).
 Loar, J. K. (2011). Chinese syntactic grammar: functional and conceptual principles. New York: Peter Lang.