Research Paper Summaries
In-depth Studies and Scholarly Contributions by Dr. Su Yeong Kim
Acquisition of the Mental State Verb Know by 2- to 5-Year-Old Children
Summary:
This study by James R. Booth, William S. Hall, Gregory C. Robison, and Su Yeong Kim (1997) explores how young children learn to understand and use the word know — a small but powerful verb that reflects one’s awareness, understanding, and beliefs. By analyzing parent–child conversations from ages two to five, the researchers trace how children’s grasp of know develops from simple recognition (“I know Mommy”) to deeper, more abstract meanings tied to thought, learning, and knowledge.
The authors found that children’s use of know evolves through clear developmental stages. At first, children use it in very concrete ways, often to describe familiarity or sensory awareness — for example, “I know that dog” or “I know this song.” As their cognitive and linguistic skills expand, they begin to use know to express understanding, such as knowing facts or reasons (“I know why it’s raining”), and eventually, evaluative uses, where know conveys reflection or judgment (“I know that’s not fair”). This growth mirrors the emergence of theory of mind — the child’s ability to understand that thoughts and knowledge can differ from reality or from what others think.
Parents play a crucial role in this process. The study showed that the frequency and richness of parents’ own use of knowclosely matched their children’s language development. Parents naturally model how to use the word across different contexts — from everyday tasks (“You know where your shoes are”) to reasoning and explanation (“Do you know why we can’t go outside?”). Children whose parents used know more frequently and flexibly tended to use it earlier and with more complex meanings. This finding highlights how language exposure acts as a scaffold for cognitive growth, teaching children not only how to speak but also how to think about knowing.
The researchers also observed that children initially used know more often to talk about their own minds than about others’. This self-centered phase gradually broadened as they grew older and started recognizing that others could “know” or “not know” something. In this way, know becomes a linguistic mirror of social understanding — children use it to describe and eventually grasp mental states beyond their own perspective.
Overall, Booth and his colleagues paint a rich picture of how a single verb traces the intertwining of language and thought. Learning know is not simply memorizing a word; it is learning to talk about knowledge itself — to mark what one understands, to reason about others, and to communicate awareness. Through everyday conversation, parents guide children up this ladder of meaning, helping them move from recognition to understanding, from self-awareness to shared knowing.
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