An investigation into the role of the input on children's acquisition of modal verbs

Abstract

Modal verbs (e.g. can and must) are complex since one form (e.g. can) may have multiple meanings (i.e. ability, permission, suggestion). Modals can be used for an epistemic purpose to reflect our level of certainty (e.g. 'it must be raining') or to express deontic meanings such as obligation or permission (e.g. 'you must go to bed') (Papafragou, 2002). Previous research has found that children typically produce modals for a deontic meaning first (Wells, 1979) however it is not clear whether children's preference for deontic modals is caused by the nature of their input or by their socio-cognitive development (e.g. Theory of Mind) (Papafragou, 1998; Tomasello, 2003). Van Dooren et al. (2017) compared children's and caregivers' uses of modals for their broad functions (i.e. epistemic or non-epistemic) but no study has yet provided a more fine-grained analysis of modal form-function mappings in the input by specifying the types of non-epistemic functions they convey (e.g. obligation and permission) and how these influence children's acquisition. In this thesis, I explore whether children's acquisition of modals is driven by the function distributions of their input. In Chapter 1, theoretical approaches to language acquisition are explored and a summary of modal verb research is provided, focusing on the areas of input frequency and the child's socio-cognitive development. This chapter ends with three emerging research questions and presents a summary of the research to be covered in the thesis centred on three to five year olds' acquisition of modals. Firstly, how does the distribution of modals with a variety of form-function mappings in the input influence children's acquisition of these same form-function mappings? Secondly, are children more likely and quicker to associate a modal with its most frequent function in the input? Thirdly, are children more likely and quicker to accept the intended interpretation of can in questions if it is contained within a sequence (e.g. can you find) that typically points to that interpretation in the input? Chapter 2 presents a corpus study examining the properties of modal use in two mother-child dyads' speech when the children were aged three and four using dense naturalistic speech samples to address research question 1. Modals were extracted and analysed according to their frequency and associated meanings, and the input and the child corpora compared using a range of novel, methodologically important controls. Chapter 3 contains two comprehension experiments which address research questions 2 and 3 in terms of whether children are more likely and quicker to associate a modal with its most frequent input function. The first deals with children's interpretations of a modal in ambiguous utterances (e.g. James can ride his bike which might refer to James's physical ability or permission to do so), assessed through a forced-choice picture selection task. The second presented children with ambiguous can questions which may function either literally (to enquire about someone's physical ability to act) or non-literally (as an instruction, e.g. can you do the laundry?). Here, we investigated whether children's acceptance of a can utterance for either meaning, as assessed in a forced-choice paradigm task, was driven by the proportional use of the sequence for either function in the input. Taken together, the results indicate that children's modal acquisition is mostly input driven in producing the most frequent form-function mappings of their input and relying on input frequency to resolve modal ambiguity in Experiment 1. The proportional bias of a sequence did not impact on participants' acceptance of can questions in Experiment 2, however children were slower to reject an appropriate can question with highly biased sequences. These findings lend support to constructivist approaches to language acquisition (Goldberg, 2006; Tomasello, 2003). Chapter 4 provides a summary of the findings and their implications, evaluates the adopted research methods and suggests avenues for future work.

Date of Award	31 Aug 2021
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Elena Lieven (Supervisor) & Anna Theakston (Supervisor)