Some studies on language acquisition display interest in subject omission. These studies mainly note the frequency of subject drop in first or second language acquisition: when and how children acquire the ability to express a subject as adult speakers do in Korean and other
languages (Clancy, 1996, 1997; Y. J. Kim, 1995, 2000; H. R. Lee, 2004) and how adults learn null subjects in Korean learning (J. T. Kim, 2003).
Clancy (1996, 1997) is influential in language acquisition research and referenced in many other studies for her theoretical framework and methodology. In particular, Clancy (1997), on collecting longitudinal records from two Korean-speaking children for a year, analyses their utterances with respect to expression of subjects and objects. The results reveal that the children show different distributions of ellipsis, pronouns and nouns. Clancy (1997) points out that certain discourse contexts affect the choices of certain reference forms and that the children somehow learn the relationships between discourse contexts and reference forms. Y. J. Kim (2000) and H. R. Lee (2004) perform similar empirical surveys, and they emphasise consideration of contexts when children learn to choose appropriate references for subject position in different discourse contexts.
The basic notion Clancy (1997) claimed is that the grammatical knowledge of Korean children is believed to be innate, but the children also learn referential choices by contextual situations. While the literature has put more weight on initial grammatical settings—that all humans are born with the grammar (e.g., Hyams, 1986) or that the grammar emerges gradually (e.g., O’Grady, Peters & Masterson, 1989)—Clancy (1997) argues that some grammatical choices are learned from experiences of encountering different contexts. More specifically, Clancy (1997) notes:
The pro-drop parameter equips children with innate, a priori expectations pertaining to ellipsis vs. overt reference, but leaves them to discover the differences between overt pronouns and noun phrases on the basis of experience. (p. 656)
Clancy (1997) further explicates that there is an inseparable link between learning argument structure and learning the importance of discourse motivations for choosing appropriate references. Notably, the study imports the significance of context into understanding referential choices in subject expression. Clancy (1997) tackles the dichotomy of subject expression (i.e., omitted or not omitted) and stresses the importance of discourse motivations for referential choice, which is also considerably appreciated in the data analysis of the current research. Y. J. Kim (2000) confirms Clancy’s (1997) findings with cross-linguistic comparison between Korean, English, Chinese, Japanese and other languages. According to her data, Korean children initially produce only predicates when they begin to speak and their use of overt subject increases rapidly until it reaches an adult’s level before they become three years old. From the
cross-linguistic perspective, she argues that all children acquiring different native languages naturally know in very early stages of language acquisition whether their language is a null- subject language and how often subjects are omitted in that language.
H. R. Lee (2004) also provides empirical data on the development of subject expression, focusing on the use of subject particles. She also conducts a longitudinal survey on the acquisition of subjects by two-year-old children, similar to Clancy (1997). H. R. Lee (2004) finds that Korean children produce all forms of subject expression in early stages of language acquisition, identical to those adult speakers produce, that is, at the age of 24 months, they already utilise null subjects, bare nominal, pronouns and subjects with particles to express subjects in sentences. Further, she finds that the children tend to speak a null-subject sentence when the subject is previously referenced in the context.
Clancy (1997), Y. J. Kim (2000) and H. R. Lee (2004) investigate the acquisition of subject expression by Korean children. They discover that Korean children become able to use subjects in the same way as Korean adult speakers do in early stages of language learning; namely, before the children turn three years old, they develop the frequency of subject omission, the use of subject particles and the use of pronoun or lexical reference. The studies agree that the acquisition of subject expression by children is affected by the caregiver’s input and context, as well as the fundamental and universal grammar being inherent.
By contrast, J. T. Kim (2003) observes the use of null subjects by an adult learner of Korean for six months. The use of null subjects in second language acquisition appears at a very early stage, according to the results. In fact, the frequency of null-subject sentences is dominant in the participant’s utterances in Korean, and it is suggested that her first language, English, does not affect the second language, Korean, in terms of subject omission, considering that English is not a pro-drop language unlike Korean. J. T. Kim (2003) interprets the results to mean that a learner assumes simple and economical grammar in language learning, and pro-drop is the economical choice in the syntactic operation of subject expression.7 Thus, even if a native speaker of a non-pro-drop language learns a pro-drop language, she resets her grammatical setting of subject expression to the more economical option (i.e., pro-drop) in very early stages
7 The theory of minimalist grammar (Chomsky, 1995) is described more systemically and delicately in J. T. Kim (2003), but I will leave it as simple as summarised here since the syntactic explanation is not our concern in this thesis.
of learning. Namely, the characteristics of the first language are not transferred into second language learning as far as the subject omission is concerned.
To summarise, J. T. Kim (2003) offers an interesting point of view that hypothesises and proves that the minimalist framework (Chomsky, 1995) of syntax is applicable to second language acquisition with regard to pro-drop. As discussed earlier, Clancy (1997), Y. J. Kim (2000) and H. R. Lee (2004) are also valuable studies that investigate the process and nature of language acquisition as well as subject expression. The studies in language acquisition support the validity of our argument on the recognition of the meaning of subject omission beyond the syntactic perspective, the consideration of contexts when dealing with subject omission and the purposeful choices among reference forms for overtly expressed subjects. Nevertheless, the main discussions in the literature continue to focus on how a language learner acquires the use of subject expression at a regular or normal level, either in the first language or in the second language. They already have a level that is set to be of an adult speaker or a native speaker and suspend examination of pragmatic meanings of subject expression.