Research

I. Linguistic theory and child language research – Truly psycholinguistic

I have been trained in both linguistics and psychology. This makes me a true psycholinguist. I believe that linguistic theories create a basis for child language research. Researchers use theories to form hypotheses that can then be tested using experiments. The obtained data can, in turn, inform us about linguistic theories. Theories are dynamic. As new discoveries are made, theories are modified and adapted to account for new data. This two-way traffic between linguistic theories and child language data has important bearings on our understanding of the nature of human language.

My work highlights the importance of theory-motivated child language research by applying experimental techniques to distinguish between theoretical accounts of child language acquisition. For example, in one of my projects, I looked at young children’s acquisition of two types of zenme(roughly corresponding to English how) questions in Mandarin Chinese, with an attempt to show how theoretical analyses of linguistic structures could raise interesting questions for child language acquisition, and how data from child language acquisition can, in turn, inform linguistic theories. The findings have important implications for distinguishing between the two major competing approaches to child language acquisition: the UG (Universal Grammar)-based approach and the usage-based approach (Li & Zhou, 2018).

In another recent project, I investigated children’s knowledge of structure dependence. According to Chomsky (1988, 2017), the computational rules of human language depend not on linear order but on structure. This core property is often referred to as structure dependence. On the theory of Universal Grammar, core properties are innately specified. Therefore, children across languages should exhibit knowledge of structure dependence as early as they can be tested (Crain 1991). To provide new cross-linguistic evidence for structure dependence, in this recent project I investigated young Mandarin-speaking children’s acquisition of two types of structures: recursive possessive constructions (Shi & Zhou, 2019) and classifier phrases (Zhao, Zhou, & Deng, 2020). The findings provide robust evidence that young Mandarin-speaking children keep to structure-dependent rules both in their productive and comprehensive use of language.

In addition, in order to test linguistic theory using child data, I devised new child-friendly experimental methods. For instance, to investigate children’s knowledge of prosodic information in sentence comprehension, I have designed and implemented a new research methodology called the Question-Statement task (Zhou & Crain, 2011). Specifically, English speakers can either make a statement or ask a question by changing the prosody, as indicated by capital letters: John bought A CHAIR?We used the Question-Statement task to see whether children are sensitive to the distinction between the question ‘John bought A CHAIR?’and the statement ‘John bought a chair’where the difference is signalled by a change in the prosodic contour assigned to the same sequence of words.

II. Child language research – A cross-linguistic approach

My research looks at both typical and atypical language development from a cross-linguistic perspective. In the area of atypical language development my research mainly focuses on two atypical populations – children with autism spectrum disorder (ASD) and children with specific language impairment (SLI). ASD is a neurodevelopmental disorder that is diagnosed on the basis of two symptom clusters: (1) persistent deficits in social communication and social interaction, and (2) restricted, repetitive patterns of behaviour, interests, or activities. It begins early in childhood and lasts throughout a person’s life. Therefore, it can cause significant social, communication and behavioural challenges. SLI is a developmental language disorder that causes an impairment in acquiring language despite otherwise normal intelligence, hearing and an adequate learning environment.

For example, in my MQRF project titled “Linguistic knowledge in children with SLI”, I investigated language development in children with SLI. Although there is now a good theory in this area, which contains mechanisms that account for the fact that typically developing (TD) children acquire language as rapidly as they do, this theory fails to explain how the language learning mechanisms permit most children to learn language relatively quickly, while they cause others to proceed very slowly. This issue is particularly obvious in children with language impairment like SLI, who are slow in acquiring language. The comparison between typical and atypical language development would shed light on this learnability question.

In addition, my research looks at language development from a cross-linguistic perspective. For example, my project titled “Using eye movements to gauge language development in preschool children”, funded by the National Social Science Foundation of China, investigates language development in both English-speaking and Mandarin-speaking preschool children. The cross-linguistic approach allows my peer researchers to test hypotheses that might not have been considered on the basis of one language alone. For example, the characteristics that distinguish SLI children from their TD peers differ from one language to the next, and this is largely due to language-specific properties. For instance, English-speaking SLI children experience well-documented deficits in the use of the grammatical morphemes that mark tense and agreement (e.g., –edand –s). By contrast, SLI children acquiring Romance languages have less trouble with verb inflections, but are highly challenged in the production of unstressed ‘clitic’ pronouns. By studying the mechanisms of these cross-linguistic findings, my research could establish early clinical markers of SLI in Mandarin Chinese (a typologically distinct language with neither tense markers nor clitic pronouns), which will then lead to improved language acquisition of children with SLI. One of the research questions I am currently seeking to answer is whether or not other parts of children’s grammar are compromised in Mandarin Chinese, as compared to Indo-European languages.

My research also compares language development in children with ASD and those with SLI. Parallels in language profiles between children with ASD and those with SLI have often been reported in previous research. For example, it has been reported that comorbid SLI is present in a subgroup of individuals with ASD, in particular in their use of grammatical morphemes that mark tense and agreement (e.g., Kjelgaard & Tager-Flusberg, 2001; Roberts et al., 2004; Tager-Flusberg & Joseph, 2003). However, it remains an open question as to whether the observed similarities in language impairments between the two populations are simply surface manifestations of the same underlying neuropsychological dysfunction, or they actually involve different underlying causes. By comparing the language profiles of the two populations, my research contributes to our understanding of this open question. Specifically, my research findings suggest that the observed similarities between the language impairments in ASD and in SLI might be superficial, and they actually involve different underlying causes and might result from distinct pathologies. All the individuals on the autism spectrum probably share certain psychological characteristics that will have potential effects on their language development.

III. Early language and cognitive development: Combining typical and atypical populations

By comparing language and cognitive development in TD children and children with ASD, my research aims to explore the relationship between language impairments and general levels of cognitive abilities, which also relates to the broader question of the relationship between language and cognition. In particular, my projects look at the whether TD children and children with ASD exhibit discrepancies between language and other cognitive abilities. The projects are funded by the National Key Project for Science and Technology Innovation Zone, and the Tsinghua University Initiative Scientific Research Program. In the projects, I mainly asked two questions: (1) Are the linguistic and cognitive systems of atypical children fundamentally similar to typical children, or are the systems fundamentally different? (2) Are their underlying neurocognitive processes and mechanisms fundamentally similar or different? To address the two questions, both behavioral (e.g., eye-tracking) and neurophysiological methods (e.g., EEG) methods were used to profile a child’s performance across linguistic and cognitive domains, the findings of which were then used to determine if the two domains are similar or discrepant in levels of performance.

For example, my research has shown that across the different dimensions of language, there are clearly relative areas of strengths and weaknesses across the autism spectrum. Some high-functioning children with ASD exhibited relative strength in the domain of lexical semantics as compared with the domain of syntax involving complex syntactic operations (Zhou et al., 2015; Zhou et al., 2017; Zhou, Zhan, & Ma, 2019). Most children with ASD showed deficits in the domains of pragmatics and prosody associated with social communication (Zhou, Zhan, and Ma, 2019; Zhou, Ma, & Zhan, 2020). In addition, although at the beginning stages of inquiry, my research has found that the degree of intelligence and Theory of Mind (ToM) do not straightforwardly predict how language development will be affected in children with ASD, attesting to a certain degree of independence between the language and other cognitive abilities. The study of children with ASD thus provides a valuable entry point into the complexities of the relationship between language and cognition and the extent to which the two dimensions of children’s development are unique or shared.