Children's ability to understand and express the concept of transitivity is crucial to their accurate interpretation of events and communication about their experiences and thoughts. Linguists propose that prototypical transitive sentences have the following structure: human agent SUBJECT + TRANSITIVE VERB + inanimate non-moving patient OBJECT (e.g. the girl broke the vase). However, it is unclear how closely children adhere to this prototype because researchers have not always sufficiently coded for, or manipulated fine-grained distinctions in noun animacy (e.g. humans vs other animates). This thesis investigates the role of animacy and prototypical transitivity in children's sentence production and comprehension over the course of development, in order to help test the validity of linguistic theory and psycholinguistic models. It also aims to bridge a link between developmental psychology and psycholinguistics by examining the extent to which infant semantic role categories are later mapped onto language. Chapter 1 discusses the theories concerning the characteristics and acquisition of the prototype. Chapter 2 reviews earlier studies on animacy in language production and comprehension before stating the rationale for additional research using a multimethodological approach. Chapter 3 presents a structural priming experiment demonstrating that dative priming does not rely on linguistic representations specifying prototypical animacy-semantic role mappings. Chapter 4 features a corpus study showing that children's simple transitives closely mirror their mothers' and the human subject - non-moving inanimate object prototype. It also includes an eye-tracking study revealing that children and adults do not strongly rely on this prototype during the online comprehension of patient nouns in active sentences. Chapter 5 summarises and evaluates these studies and discusses the implications of the findings for linguistic theory, psycholinguistic models and developmental psychology. It also outlines possible future studies for further insight into the roles of animacy and prototypical transitivity in language.