4. General Discussion

This study had two important goals. First, we wanted to chart the developmental trajectory of early vocabulary acquisition in Mandarin Chinese based on a large-scale parental report study, as has been previously done for English by Bates and colleagues (Bates et al., 1994; Caselli et al., 1995). In this respect we wanted to see if Mandarin-learning children follow a universal pattern of lexical development, as children learning other languages, or if they show language-specific patterns that differ from those in English and other European languages. Second, we wanted to understand the important contributing factors that are responsible for the age of acquisition of lexical categories across the early stages of lexical development. With respect to the first goal, our results show that(i) social words, especially words for people, are the predominate type of words in Chinese-speaking children’s earliest productive vocabulary; (ii) overall, Chinesespeaking children’s vocabulary contains greater proportions of nouns than other word categories, especially at the earliest vocabulary stage; and (iii) verbs tend to appear earlier for Chinese-speaking children as compared with English-speaking children at the same levels of vocabulary development. These results address the three specific questions we raised in the ‘Introduction’ with regard to the developmental trajectories of child Mandarin lexicon. With respect to the second goal, the correlation and multiple regression analyses show that it is the interplay between conceptual (imageability) and linguistic variables (word frequency, word length, and grammatical category) that jointly determine the AoA of Mandarinspeaking children’s early vocabulary.

4.1 First words and kinship terms in early child Mandarin

The data in the present study provide the first clear evidence that social words predominate in Chinese-speaking children’s earliest vocabulary, and the majority of social words in our study are words for people. This statement is verified by two findings: (i) as illustrated in Figure 1(a), words for people occupy more than 60% of the vocabulary when the lexicon contains less than 10 words (i.e. word types), and (ii) there are seven words representing kinship terms among the ten earliest acquired words, as Table 2 shows. These findings are consistent with the results from children speaking German (Kauschke & Hofimeister, 2002), Italian (Caselli et al., 1995; D’Odorico et al., 2001), and English (Caselli et al., 1995). Our results, together with the findings from other studies, suggest that social words make up the first category in children’ expressive vocabulary regardless of the language.

The predominance of kinship terms in early child Mandarin vocabulary may be specially related to the richness of kinship terms in the Chinese language and the emphasis on kinship relations in Chinese family culture. In Chinese, close relatives have specific names depending on whether they are from the maternal or paternal side, their gender, and relative age (see also Tardif et al., 2008). A somewhat extreme example is the word cousin in English that translates to eight terms in Chinese: tang2xiong1 ‘son of father’s brother, older than the speaker’, tang2di4 ‘son of father’s brother, younger than the speaker’, biao3ge1 ‘son of mother’s brother, older than the speaker’, biao3di4 ‘son of mother’s brother, younger than the speaker’, tangjie ‘daughter of father’s brother, older than the speaker’, tangmei ‘daughter of father’s brother, younger than the speaker’, biaojie‘daughter of mother’s brother, older than the speaker’, biaomei ‘daughter of mother’s brother, younger than the speaker’. On the other hand, Chinese also has some kinship terms that serve more general purposes, instead of labeling direct kinship relationship. For example, yeye refers to grandpa literally, but also may be used to refer to any male with roughly the same age as speaker’s own grandpa. Unlike American mothers favoring object naming games (Bornstein, Haynes & Painter, 1998; Fernald & Morikawa, 1993; Goldfield, 1993; Tamis-LeMonda, Bornstein, Cyphers, Toda & Ogino, 1992; Tardif et al., 1997), Chinese families encourage children to practice name calling in appropriate ways with various kinship terms for addressing relatives and acquaintances. Given these unique characteristics in Chinese language and culture, it is only natural that Chinese children’s earliest vocabulary contains a large number of kinship terms. Tardif et al. (2008) also showed that there are eight to nine kinship terms among the top twenty words produced by Mandarin- and Cantonese-speaking children, while there are only two in comparable English-speaking children’s samples.

This precedence and predominance of kinship words seem to contradict the predictions of some existent theories regarding the order of acquisition of words. The ‘Division of Dominance’ theory (Gentner & Boroditsky, 2001) and the‘SICI Continuum’ theory (Maguire et al., 2006) are two hypotheses that make explicit predictions about the acquisition sequence of different word categories. According to these hypotheses, relational nouns such as uncle and grandmother should be acquired after the proper nouns (e.g. Mary, Sue) and concrete nouns(e.g. ball, spoon), because the former denote relations between people and are harder for children to acquire than the latter. However, both the present study and Tardif et al. (2008) find a large number of relational kinship terms in Mandarinand Cantonese-speaking children’s earliest vocabulary. Of course, one could argue that, despite the appearance of the words in children’s early vocabulary, very young children may not understand the exact meanings of the kinship terms, and only later on can they start to appreciate the complex relations that hold among the different people as denoted by these terms. This is certainly a hypothesis that needs to be tested empirically in future research.

4.2 Developmental changes in vocabulary composition across stages

Overall, our data and analyses show that the vocabulary development trajectory for Chinese-speaking children fits the four-stage model of lexical development proposed by Caselli et al. (1999). At the very first stage of lexical development, especially when children’s vocabulary is within ten to twenty words, onomatopoeic terms, social routines, and names for favorite people are predominant. Some social routine words such as bu ‘no’ and xiexie ‘thanks’, also appear in the earliest vocabulary.

The second stage, according to Caselli et al. (1999), is REFERENCE, when children’s vocabulary accumulates to 50 to 200 words. During this stage, in English and in many other Indo-European languages, the vast majority of words are nominals; common nouns and proper nouns referring to objects, things, and people. Chinese-speaking children’s vocabulary development is also characterized by the rapid growth of nominals. When the size of vocabulary goes beyond twenty words, common nouns quickly outnumber social words and become the largest category in children’s lexicons.

The third stage is the so-called PREDICATION, according to Bates and colleagues (Bates et al., 1994; Caselli et al., 1995, 1999), where verbs and adjectives show substantial increases after children have acquired 100 or more words. Here Chinese-speaking children demonstrate some different developmental patterns in the acquisition of predicates when compared with their English and Italian peers: (i) the percentage of predicates is higher throughout the early vocabulary in Mandarin-speaking children than in Italian- or English-speaking children, and (ii) the percentage of predicates at each vocabulary level is constant, roughly around 30% out of the total vocabulary (see Figure 2), whereas the percentage of predicates increases from less than 10% up to 25% for Italian or English children. It has been argued that increases in predicates are closely related to the development of an ability to understand relational meanings (Caselli et al., 1999). The overall higher percentage of predicates in Chinese seems to contradict this argument, but upon detailed examination of the actual predicate words produced by Chinese-speaking children, we can see that the Chinese verbs are mostly words of higher imageability or concrete actions: for example, fei ‘fly’, ku ‘cry’, and chi ‘eat’ when their total vocabulary is between 101 and 200. Only a small percentage of children can produce some verbs that encode relational meaning: for example, 21% of the children produced zhui ‘chase’ and 17% of the children produced tui ‘push’ at this time. The overall higher percentage of verbs in Chinese children’s speech as compared with other languages is probably due to the higher imageability and shorter syllable lengths that characterize many Chinese verbs (see Liu et al., 2008, and further discussion below).

Finally, the fourth stage is GRAMMAR, according to Caselli et al. (1999), at which time grammatical function words develop when the size of the vocabulary grows between 300 and 500 words. However, the Chinese-speaking children in the present study do not display substantial growth in grammatical function words, even at the relatively late stages. Examining the closed-class words when children’s overall vocabulary exceeds 400 words, we find that more than half of the children could not produce half of the closed-class words. Some highly frequent closed-class words in adult spoken language are rarely used by children: for example, only 10% of the children are reported to produce connecting words such as ruguo ‘if’, and only 30% of children are reported to produce helping verbs such as bixu ‘must’. Children at this stage also have trouble producing plural pronouns, such as women ‘we’, nimen ‘you’, zhexie ‘these’, naxie ‘those’. One speculation about the lack of progress with closed-class words in Chinese-speaking children is that the Chinese language relies heavily on semantic-pragmatic-contextual cues (Li, 1998), and as such function words are less important, especially in child-directed speech, and hence less likely to be picked up by children during early stages of lexical development.

When describing the developmental changes in Chinese-speaking children’s lexical composition, we should highlight that, despite the language-specific differences between Chinese and other languages, NOUNS ARE LEARNED BEFORE VERBS, EVEN IN CHINESE. We quantify this claim based on several considerations. First, Gentner’s (1982) original noun bias proposal includes common nouns and proper nouns. Our analysis above shows that, although the vast majority of the words are social words when children acquire less than twenty words, a large number of these words are kinship terms in Chinese, which are often used by children as proper nouns to name particular listeners in the speech environment. Moreover, the percentage of common nouns quickly exceeds that of social words after twenty words. Second, after children have acquired fifty words, common nouns occupy almost half of the lexicon at each vocabulary level in child Mandarin. These results are consistent with the claims that nominals (including proper nouns and common nouns) are first acquired by children and that common nouns are the predominant category overall. Third, although the first verbs appear as early as common nouns do for Chinese-speaking children, the percentage of common nouns is significantly higher than that of verbs at every vocabulary level(see Figure 1(a) and 2). This pattern is consistent with several recent studies of Chinese-speaking children’s vocabulary development (Liu, 2007; Liu et al., 2008; Tardif, 2006).

While it does indeed appear to be a universal pattern that nouns are learned before verbs, our analyses above also show significant differences between Chinese and English and other languages. In fact, based on our above analysis of the developmental stages of early vocabulary according to Caselli et al.(1999), we can see that in three of the four stages Chinese-speaking children are influenced by the language- or culture-specific characteristics (more social words, more predicates, and fewer closed-class words as compared with the numbers in English), especially with respect to the early verb advantage. Compared with other languages, verbs appear at the earliest stage of lexical development in child Mandarin, as has been reported in other verb-friendly languages (Brown, 1998; Gopnik & Choi, 1995; Tardif, 1996).

Tse, Chan and Li (2005) also reported a much stronger verb advantage in Cantonese-speaking children. However, it seems that the differences between the current Mandarin data and Tse et al.’s Cantonese data may be due to the age of samples and the data collection methods, in addition to possible cultural and linguistic differences between Cantonese and Mandarin. First, the children in Tse et al.’s study were preschoolers and much older than the children in our study(aged between 3;0 and 5;10). These children may be at the stage of producing sophisticated sentences in which verbs serve as the pivot, and therefore may have experienced more accelerated growth of verbs than children at earlier stages. An interesting possibility that follows from here is that one might observe a stronger verb advantage as the children become older. Second, with regard to methods of data collection, the data of Tse et al., were based on recordings of 30-minute free play sections, while our study was based on cross-sectional parental reports. Spontaneous speech within a limited time session may depend heavily on the free play context in which children tend to produce more verbs than nouns (Tardif et al., 1999).

In sum, we must conclude that both language-specific properties and universal mechanisms are responsible for the pattern we find in Chinese-speaking children’s vocabulary development.

4.3 Factors affecting the age of acquisition of vocabulary

In addition to describing the developmental trajectories of early vocabulary, we have identified a number of conceptual and linguistic factors that influence the age of acquisition of words based on our analysis.

Input frequency. Input frequency has been explored extensively in child language, and in general it is accepted that higher-frequency words tend to be learned earlier than lower-frequency words by children. The close relationship between word frequency and AoA (mostly based on adults' subjective ratings) has also been carefully investigated in the adult word reading literature, in which a strong negative correlation (from -0.40 to -0.71) is usually reported (see reviews Juhasz, 2005, and Hernandez & Li, 2007). Our multiple regression analysis also confirms that word frequency is a crucial factor in modulating the AoA of words. Our results are also consistent with some previous studies of the relationship between language input and vocabulary acquisition in Chinese-speaking children. Specifically, Tardif et al. (1997, 1999) analyzed parental language input and found that Chinese caregivers tended to produce more verb types and verb tokens than English-speaking caregivers, which the authors interpreted as a significant contributor to the early verb advantage in child Chinese. Zhao and Li’s (2008) simulation results also showed that early acquired words in their model had higher frequency, and the number of high-frequency verbs was larger in Chinese than in English.

One could argue that the word frequency norms used here (based on subtitles) are not good estimates of language input to infants and toddlers as estimates based on child-directed parental speech such as those available in the CHILDES database (MacWhinney, 2000). Although child-directed parental speech from CHILDES has been successfully used as estimates of input in previous studies (e.g. Goodman et al., 2008), we did not use frequency counts based on the CHILDES parental speech in this study due to the very small sample of corpora available for Mandarin Chinese in CHILDES. Additionally, one could take a more broad view of the language environment in which the child grows up, especially with regard to overhead adult-adult conversations, and speech interactions from the TV, etc. (e.g. Akhtar, Jipson & Callanan, 2001), and in this view, perhaps the subtitle frequency norms can indeed serve as good approximations of the linguistic input to children.

Word length. Word length is another important factor, especially at the earliest stage of vocabulary development. In Figure 3, we showed that the percentage of monosyllabic verbs is notably higher than that of multisyllabic verbs, whereas for nouns, the reverse pattern is observed: children produce more multisyllabic nouns than monosyllabic nouns after they reach age 1;10 (or 100~200 vocabulary mark). In our checklist, multiple syllabic verbs occupy only 29% of the total vocabulary. We argue that word length here would provide more advantage to verbs than to nouns for child learning.

There have been some earlier studies indicating that monosyllabic items predominate early stages (from 1;5 to 2;2), and longer words gradually appear at later stages of testing intervals (Maekawa & Storkel, 2006; Storkel, 2004; Waterson, 1971, 1978). Maekawa and Storkel (2006) also found a strong influence of word length on English-speaking children’s early word learning, and suggested that word length constrains children’s word learning by affecting working memory processes necessary to hold the phonological form at the outset of word learning. Furthermore, Zhao and Li’s (2008) simulated vocabulary development in English and Chinese with a computational model, and also found that early acquired words tended to be words with shorter phonemic length in both languages. Together, these studies and ours show that specific linguistic properties of words siginificantly impact early vocabulary development.

Imageability. The SICI theory (Maguire et al., 2006), as discussed in the‘Introduction’, highlights the contribution of four factors to early vocabulary development: Shape, Individuation, Concreteness, and Imageability of the objects to which words refer. As such, the SICI theory provides useful dimensions for us to think about the role of the non-linguistic conceptual properties of words, as opposed to the linguistic properties of words. In this study, we tested the role of the imageability of objects encoded by words, and found that: (i) Chinese nouns are more imageable than verbs; (ii) imageability is significantly correlated with the AoA of words; and (iii) imageability can uniquely account for the variances in the AoA of words in the early Mandarin lexicon.

Our findings on imageability were consistent with previous studies in English (Ma et al., 2009; McDonough et al., 2011) and in Chinese (Ma et al., 2009). As compared with Ma et al.,’s and McDonough et al.,’s studies, our study had a larger sample of words and included more variables. Nevertheless, in all studies, including ours, imageability was confirmed as having a significant unique contribution in predicting the AoA of early words. The question of why highimageability words are acquired earlier than low-imageability words has been addressed by several researchers (Golinkoff & Hirsh-Pasek, 2006; Maguire et al., 2006; Tulving & Thomson, 1973). For example, words with high imageability denote objects or actions that tend to be perceptually salient and accessible, easier to represent or retrieve, may appear earlier in life, and hence be acquired easier. However, detailed studies of the correlations of imageability with concreteness, as well as the interaction between imageability and shape, individuation, and concreteness, should be conducted further across a larger range of lexical development.

Grammatical category. Grammatical category membership (noun or verb) is also found to account for a small but significant amount of variance in the AoA of early words in our regression analysis. Chinese-speaking children acquired fewer verbs than nouns across the various stages of vocabulary development. In the literature, researchers have provided several reasons to account for why nouns and verbs may differ on conceptual difficulty (Gentner, 2006; Parish-Morris, Pruden, Ma, Hirsh-Pasek & Golinkoff, 2010). Specifically, verb learning requires children to detect which semantic components should be packaged into the meaning of a verb (Tomasello, 1995). Semantic components encoded into the concepts of verbs differ depending on the instruments (e.g. comb, vacuum), manner of the motion(e.g. jump, float), path of the motion (e.g. approach, ascend), etc. Moreover, languages differ in what semantic components are packaged into their verbs(Gentner & Boroditsky, 2001), and such complexities require an extended time for children to understand how their language typically encode verbs. However, such conceptual difficulties may be reduced by the distinct linguistic properties of Chinese. For example, the observed verb advantage in Chinese-speaking children may benefit in part from the short word length and higher input frequencies, as discussed earlier, and in part from the easy accessibility of the concepts that Chinese verbs label (e.g. the English verb carry can be expressed by several different Chinese verbs like bao, bei, kang, ti, etc.; see a detailed discussion in Saji, Imai, Saalbach, Zhang, Shu & Okada, 2011).

In summary, our study provides a first detailed, large-scale analysis of the developmental patterns underlying early vocabulary acquisition in Mandarin Chinese. We have identified four key factors relevant to the age or order of acquisition of words, specifically conceptual property (imageablity), word frequency, word length and grammatical category of the input language. In doing so, we hope to provide insights into current debates regarding cross-linguistic similarities and differences in the acquisition of nouns, verbs, adjectives, and closed-class words during the early years of child language development.

References

Akhtar, N., Jipson, J. & Callanan, M. A. (2001). Learning words through overhearing. Child Development, 72(2), 416-430.

Au, T., Dapretto, M. & Song, Y.-K. (1994). Input vs. Constraints: Early word acquisition in Korean and English. Journal of Memory and Language, 33, 567-582.

Barca, L., Burani, C. & Arduino, L. S. (2002). Word naming times and psycholinguistic norms for Italian nouns. Behavior Research Methods, Instruments & Computers, 34, 424-434.

Bates, E., Marchman, V., Thal, D., Fenson, L., Dale, P., Reznick, J. S., Reilly, J. & Hartung, J. (1994). Developmental and stylistic variation in the composition of early vocabulary. Journal of Child Language, 21, 85-123.

Behrens, H. (1998). How difficult are complex verbs? Evidence from German, Dutch, and English. Linguistics, 36, 679-713.

Bird, H., Franklin, S. & Howard, D. (2001). Age of acquisition and imageability ratings for a large set of words, including verbs and function words. Behavior Research Methods, Instruments & Computers, 33, 73-79.

Bloom, L., Tinker, E. & Margulis, C. (1993). The words children learn: Evidence against a noun bias in early vocabularies. Cognitive Development, 8, 431-450.

Bornstein, M. & Cote, L. R. (2004). Cross-linguistic analysis of vocabulary in young children: Spanish, Dutch, French, Hebrew, Italian, Korean, and American English. Child Development, 75, 1115-1139.

Bornstein, M. H., Haynes, O. M. & Painter, K. M. (1998). Sources of child vocabulary competence: A multivariate model. Journal of Child Language, 25, 367-393.

Brown, P. (1998). Children’s first verbs in Tzeltal: Evidence for an early verb category. Linguistics, 36(4), 715-753.

Brysbaert, M., Buchmeier, M., Conrad, M., Jacobs, A.M., Bölte, J. & Böhl, A.(2011). The word frequency effect: A review of recent developments and implications for the choice of frequency estimates in German. Experimental Psychology, 58, 412-424.

Cai, Q. & Brysbaert, M. (2010). SUBTLEX-CH: Chinese word and character frequencies based on film subtitles. PLoS ONE, 5, e10729; online http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0010729.

Caselli, M. C., Bates, E., Casadio, P., Fenson, J., Fenson, L., Sanderl, L. & Weir, J. (1995). A cross-linguistic study of early lexical development. Cognitive Development, 10, 159-199.

Caselli, M. C., Casadio, P. & Bates, E. (1999). A comparison of the transition from first words to grammar in English and Italian. Journal of Child Language, 26, 69-111.

Choi, S. & Gopnik, A. (1995). Early acquisition of verbs in Korean: A crosslinguistic study. Journal of Child Language, 22, 497-529.

Cohen, J., Cohen, P., West, S. G. & Aiken, L. S. (2003). Applied multiple regression/ correlation analysis for the behavioral sciences (3rd ed.). Mahwah, NJ: Lawrence Erlbaum Associates.

Cuetos, F., Glez-Nosti, M., Barbon, A. & Brysbaert, M. (2011). SUBTLEX-ESP: Spanish word frequencies based on film subtitles. Psicologica, 32, 133-143.

Dale, P. (1991). The validity of a parent report measure of vocabulary and syntax at 24 months. Journal of Speech and Hearing Sciences, 34, 563-571.

Dale, P., Bates, E., Reznick, S. & Morisset, C. (1989). The validity of a parent report instrument of child language at twenty months. Journal of Child Language, 16, 239-250.

D’Odorico, L., Carubbi, S., Salerni, N. & Calvo, V. (2001). Vocabulary development in Italian children: a longitudinal evaluation of quantitative and qualitative aspects. Journal of Child Language, 28, 351-372.

Fenson, L., Dale, P., Reznick, J. S., Thal, D., Bates, E., Hartung, J., et al. (1993). MacArthur Communicative Development Inventories: User’s guide and technical manual. San Diego, CA: Singular.

Fernald, A. & Morikawa, H. (1993). Common themes and cultural variations in Japanese and American mothers’ speech to infants. Child Development, 64, 637-656.

Gentner, D. (1982). Why nouns are learned before verbs: linguistic relativity versus natural partitioning. In S. A. Kuczaj (ed.), Language development: Vol. 2. Language, thought and culture (pp. 301-334). Hillsdale, NJ: Erlbaum.

Gentner, D. (2006). Why verbs are hard to learn, In K. Hirsh-Pasek & R. Golinkoff(eds.), Action meets word: How children learn verbs (pp. 544-564). Oxford: Oxford University Press.

Gentner, D. & Boroditsky, L. (2001). Individuation, relativity, and early word learning. In M. Bowerman & S. C. Levinson (eds.), Language, culture & cognition: Vol. 3. Language acquisition and conceptual development (pp. 215-256). New York: Cambridge University Press.

Gillette, J., Gleitman, H., Gleitman, L. & Lederer, A. (1999). Human simulations of vocabulary learning. Cognition, 73, 135-176.

Gleitman, L. R. & Gleitman, H. (1994). A picture is worth a thousand words, but that’s the problem. In B. Lust, M. Suner & J. Whitman (eds.), Syntactic theory and first language acquisition: Cross-linguistic perspectives. Vol. 1: Heads, projections, and learnability (pp. 291-299). Hillsdale, NJ: Erlbaum.

Goldfield, B. A. (1993). Noun bias in maternal speech to one year olds. Journal of Child Language, 20, 85-99.

Golinkoff, R. M. & Hirsh-Pasek, K. (2006). Baby wordsmith: from associationist to social sophisticate. Current Directions in Psychological Science, 15, 30-33.

Golinkoff, R. M., Mervis, C. V. & Hirsh-Pasek, K. (1994). Early object labels: The case for a developmental lexical principles framework. Journal of Child Language, 21, 125-155.

Goodman, J. C., Dale, P. S. & Li, P. (2008). Does frequency count? Parental input and the acquisition of vocabulary. Journal of Child Language, 35, 521-559.

Gopnik, A. & Choi, S. (1995). Names, relational words, and cognitive development in English-and Korean-speakers: nouns are not always learned before verbs. In M. Tomasello & W. Merriman (eds.), Beyond names for things: Young children’s acquisition of verbs (pp. 63-80). Hillsdale, NJ: Lawrence Erlbaum.

Hao, M., Shu, H., Xing, A. & Li, P. (2008). Early vocabulary inventory for Mandarin Chinese. Behavior Research Methods, 40, 728-733.

Hernandez, A. & Li, P. (2007). Age of acquisition: Its neural and computational mechanisms. Psychological Bulletin, 133, 638-650.

Juhasz, B. (2005). Age-of-acquisition effects in word and picture identification. Psychological Bulletin, 131(5), 684-712.

Kauschke, C. & Hofmeister, C. (2002). Early lexical development in German: A study on vocabulary growth and vocabulary composition during the second and third year of life. Journal of Child Language, 29, 735-757.

Keuleers, E., Brysbaert, M. & New, B. (2010). SUBTLEX-NL: A new frequency measure for Dutch words based on film subtitles. Behavior Research Methods, 42(3), 643-650.

Kim, M., McGregor, K. K. & Thompson, C. K. (2000). Early lexical development in English- and Korean-speaking children: language-general and languagespecific patterns. Journal of Child Language, 27, 225-254.

Kong, L., Hu, D., Ouyang, J., Chen, C., Ding, L., Wang, X., Zhu, W., Fu, M. & Yao, W. (2004). 汉族儿童实词习得研究[Research on the acquisition of content words in Chinese-speaking children]，合肥：安徽大学出版社[Hefei: Anhui University Press].

Li, P. (1998). Crosslinguistic variation and sentence processing: The case of Chinese. In D. Hillert (ed.), Sentence processing: A crosslinguistic perspective. (Vol. 31 of Syntax and Semantics; pp. 33-51). San Diego, CA: Academic Press.

Li, P., Zhao, X. & MacWhinney, B. (2007). Dynamic self-organization and early lexical development in children. Cognitive Science, 31(4), 581-612.

Liu, S. X. (2007). Early lexical development in English, Mandarin, and Cantonese: A cross-linguistic study based on CHILDES. (Unpublished MA thesis) University of Richmond.

Liu, S. X., Zhao, X. W. & Li, P. (2008). Early lexical development: A corpus-based study of three languages. In B. C. Love, K. McRae & V. M. Sloutsky (eds.), Proceedings of the 30th Annual Conference of the Cognitive Science Society(pp. 1343-1348). Austin, TX: Cognitive Science Society.

Liu, Y., Shu, H. & Li, P. (2007). Word naming and psycholinguistic norms: Chinese. Behavior Research Methods, 39, 192-198.

Ma, W., Golinkoff, R. M., Hirsh-Pasek, K., McDonough, C. & Tardif, T. (2009). Imageability predicts the age of acquisition of verbs in Chinese children. Journal of Child Language, 36, 405-423.

MacWhinney, B. (2000). The CHILDES Project: Tools for Analyzing Talk. Mahwah, NJ: Lawrence Erlbaum Associates.

Maekawa, J. & Storkel, H. L. (2006). Individual differences in the influence of phonological characteristics on expressive vocabulary development by young children. Journal of Child Language, 33, 439-459.

Maguire, M. J., Hirsh-Pasek, K. & Golinkoff, R. M. (2006). A united theory of word learning: Putting verb acquisition in context. In K. Hirsh-Pasek & R. M. Golinkoff (eds.), Action meets word: How children learn verbs (pp. 364-391). Oxford: Oxford University Press.

Markman, E. M. (1987). How children constrain the possible meanings of words. In U. Neisser (ed.), Concepts and conceptual development: Ecological and intellectual factors in categorization (pp. 255-287). New York: Cambridge University Press.

McDonough, C., Song, L., Hirsh-Pasek, K., Golinkoff, R. M. & Lannon, R. (2011). An image is worth a thousand words: Why nouns tend to dominate verbs in early word learning. Developmental Science, 14, 181-189.

Nelson, K. (1973). Structure and strategy in learning to talk. Monograph of the Society for Research in Child Development, 38, 1-135.

New, B., Brysbaert, M., Veronis, J. & Pallier, C. (2007). The use of film subtitles to estimate word frequencies. Applied Psycholinguistics, 28, 661-677.

Parish-Morris, J., Pruden, S. M., Ma, W., Hirsh-Pasek, K. & Golinkoff, R. M.(2010). A world of relations: Relational words. In B. C. Malt, and P. Wolff(eds.) Words and the mind: How words capture human experience (pp. 219-242). Oxford: Oxford University Press.

Pine, J. M. & Lieven, E. V. (1990). Referential style at thirteen months: why age

defined cross-sectional measures are inappropriate for the study of strategy differences in early language development. Journal of Child Language, 17, 625-631.

Saji, N., Imai, M., Saalbach, H., Zhang, Y., Shu, H. & Okada, H. (2011). Word learning does not end at fast-mapping: evolution of verb meanings through reorganization of an entire semantic domain. Cognition, 118(1), 45-61.

Sandhofer, C., Smith, L. & Luo, J. (2000). Counting nouns and verbs in the input: Differential frequencies, different kinds of learning? Journal of Child Language, 27, 561-585.

Storkel, H. L. (2004). Methods for minimizing the confounding effects of word length in the analysis of phonotactic probability and neighborhood density. Journal of Speech Language and Hearing Research, 47, 1454-1468.

Tamis-LeMonda, C. S., Bornstein, M. H., Cyphers, L., Toda, S. & Ogino, M.(1992). Language and play at one year: A comparison of toddlers and mothers in the United States and Japan. International Journal of Behavioral Development, 15, 19-42.

Tardif, T. (1996). Nouns are not always learned before verbs: evidence from Mandarin speakers’ early vocabularies. Developmental Psychology, 32, 492-504.

Tardif, T. (2006). But are they really verbs? Chinese words for action. In K. HirshPasek & R. Golinkoff (eds.), Action meets word: How children learn verbs(pp. 477-498). Oxford: Oxford University Press.

Tardif, T., Fletcher, P., Liang, W., Zhang, Z., Kaciroti, N. & Marchman, V. A.(2008). Baby’s first 10 words. Developmental Psychology, 44, 929-938.

Tardif, T., Gelman, S. A. & Xu, F. (1999). Putting the ‘noun bias’ in context: a comparison of English and Mandarin. Child Development, 70, 620-635.

Tardif, T., Shatz, M. & Naigles, L. (1997). Caregiver speech and children’s use of nouns versus verbs: a comparison of English, Italian, and Mandarin. Journal of Child Language, 24, 535-565.

Tomasello, M. (1995). Pragmatic contexts for early verb learning. In M. Tomasello& W. E. Merriman (eds.), Beyond the name for things: Young children’s acquisition of verbs (pp. 115-146). Hillsdale, NJ: Lawrence Erlbaum.

Tse, S. K., Chan, C. & Li, H. (2005). Is the expressive vocabulary of young Cantonese speaker noun or verb dominated? Early Child Development and Care, 175, 215-227.

Tulving, E. & Thomson, D. M. (1973). Encoding specificity and retrieval processes in episodic memory. Psychological Review, 80, 352-373.

Waterson, N. (1971). Child phonology: a prosodic view. Journal of Linguistics, 7, 179-211.

Waterson, N. (1978). Growth of complexity in phonological development. In N. Waterson & C. Snow (eds.), The development of communication (pp. 415-442). New York: Wiley.

Waxman, S. R. & Booth, A. E. (2003). The origins and evolution of links between word learning and conceptual organization: new evidence from 11-montholds. Developmental Science, 6, 130-137.

Zhao, X. W. & Li, P. (2008). Vocabulary development in English and Chinese: A comparative study with self-organizing neural networks. In B. C. Love, K. McRae & V. M. Sloutsky (eds.), Proceedings of the 30th Annual Conference of the Cognitive Science Society (pp. 1900-1905). Austin, TX: Cognitive Science Society.