It does not require that they do so by any particular method, but the child seeking to learn the language must somehow come to associate words with objects and actions in the world.
The relationship between semantic and syntactic categories can then be used to iteratively create, test, and refine internal grammar rules until the child's understanding aligns with the language to which they are exposed, allowing for better categorization methods to be deduced as the child obtains more knowledge of the language.
[1] The semantic bootstrapping theory was first proposed by Steven Pinker in 1982 as a possible explanation of how a child can formulate grammar rules when acquiring a first language.
[1] A child acquiring a first language possesses, at all stages, an expectation that words will fall into specific grammatical categories.
The child does not possess, however, an innate knowledge of how syntactic categories are expressed in the language they are acquiring.
[1] Rondal and Cession[6] tested the viability of the semantic bootstrapping hypothesis by observing the speech of 18 monolingual English speaking mothers to their normally developing children age 1 to 2 years old.
The focus of the experiment was to find out whether the grammatical and semantic categories and relations were correlated in the speech children heard.
Rondal and Cession suggested that the input evidence assists children to identify those grammatical function categories by using thematic relations (agent, patient, etc.).
[6] They found that semantic notions reliably correlate with specific syntactic elements in parental speech and this may support the child’s construction of grammatical categories.
The major findings of Gropen et al.’s experiments illustrated that both children and adults showed no tendency to express the figure entity as the direct object when faced with a locative verb.
Similarly, in the experiment done by Kim et al., children and adults were tested whether they could describe an event using a specific locative verb provided by the experimenters.
Children's lack of errors with manner of motion verbs suggests that they are subject to the same constraint that shapes cross linguistic variability.
[9] This is sometimes construed as being incompatible with semantic bootstrapping, which proposes that verb meanings can be identified from the extralinguistic context of use.
[10] Lila Gleitman argues that word learning is not as easy as the semantic bootstrapping hypothesis makes it seem.
[9] Siegel argues that the semantic bootstrapping hypothesis can not account for how children acquire case marking in split ergative languages.
[11] Ambridge et al. argues against the existence of a universal grammar and in turn against the plausibility of semantic bootstrapping.