The aim of this thesis was to examine children’s development as language users, with a focus on their development as conversationalists. Conversational development was measured through conversational contingency, i.e. how conversational turns are connected to each other, either in topic or time. The thesis introduces a conversational contingency hierarchy, including basic conversational contingency (turns that in any way acknowledges the topic of the previous turn), which constitutes the main outcomes measure in the conducted studies. The thesis consists of four papers. Paper I-III were conducted with Swedish speaking children from the longitudinal MINT project (n=40; n=50; n=63). The first paper investigated which factors, internal and external to the child, that best predicted conversational contingency of children age five. The studies included linguistic and cognitive measures, environmental factors, as well as social and cognitive measures in early development. Results showed that receptive vocabulary (but not morphosyntactic accuracy) was related to positive conversational measures, as was later preschool entry. A suggested explanation is that a child needs to reach a specific level of lexical knowledge to start to understand conversational conventions. Paper II investigated the development of conversational behaviour at age seven. Conversational measures were analysed with measures of core language, executive functions (EF), and specific pragmatic abilities. Results showed that the conversational measures at age seven were no longer predicted by receptive vocabulary. Instead there were correlations to working memory, cognitive flexibility, and comprehension of conversational implicatures. A key finding was that measures of basic conversational contingency increased substantially from age five to seven. The results indicate that certain abilities affect conversational development during certain stages of development. Paper II also shows that basic conversational contingency develops gradually towards the adult conversational norm. Paper III examined the size, velocity, and acceleration of the parental reported productive vocabulary and if these measures predicted later core language and language use/pragmatic skill. Parental reports of productive vocabulary informed later language ability (receptive vocabulary and morphosyntactic accuracy), but not to the same extent as in previous research. The results indicate that the early lexicon does not inform later language use. Paper IV investigated older children, ages 11–12, 15–16, and the development of audience design (AD). We measured the ability to tailor referential expressions in accordance with the inferred world knowledge of an addressee. Measures of EF were also obtained. Results showed that AD develops during adolescence, and provided indications for a separation of world knowledge-based AD from EF. Additionally, the study shows that aspects of pragmatic competence are still under development well into adolescence.  In sum, the thesis concludes that the relationship between conversational development and other developmental factors is dynamic and multifaceted. The ability to acknowledge the turns of others develops in tandem with several other abilities. Specific phases during conversational development connect to core language, executive functions, and comprehension of implicatures.

When in conversation, a child may respond to an adult’s turn in different ways: by saying something that acknowledges what was previously said, saying something that furthers the topic of the conversation, saying something off topic, or by not saying anything at all. Different types of responses like these have been investigated with typically developing preschoolers and older children with autism but we still understand relatively little about what predicts their use. With a longitudinal sample of 40 Swedish-speaking five-year-olds, we carried out three studies investigating which factors, internal and external to the child, were the best predictors of the above four different aspects of children’s conversational behaviour. In Study 1, we investigated the predictive value of broadly concurrent linguistic and cognitive measures and found that receptive vocabulary was related to appropriate conversation responses. In Study 2, we investigated the predictive value of environmental factors and found that later preschool entry was positively related to contingent responses in this relatively socially advantaged sample. Finally, in Study 3, we investigated the predictive value of social and cognitive factors measured in early development  and found no reliable relations. Together, these exploratory studies suggest that different aspects of children’s conversational skills may depend on strong lexical comprehension and may be facilitated by the caregiving environment.

The ability to adapt utterances to the world knowledge of one’s addressee is undeniably ubiquitous in human social cognition, but its development and association with other cognitive mechanisms during adolescence have not been studied. In an online production task, we measured the ability of children entering adolescence (ages 11–12, M= 11.8, 𝑁=29,17girlsN=29, 17 girls) and adolescents (ages 15–16, M = 15.9, 𝑁=29,17girlsN=29, 17 girls) to tailor referential expressions in accordance with the inferred world knowledge of their addressee—an ability we refer to as world knowledge-based audience design (AD). A post-test survey showed that both age groups held similar assumptions about the addressees’ knowledge of referents, but the younger age group did not consistently adapt their utterances in accordance with these assumptions during online production, resulting in a significantly improved AD behaviour across age groups. We also investigated the reliance of AD on executive functions (EF). Executive functioning (as reflected by performance on the Wisconsin card sorting task) increased significantly with age, but did not explain the age-related increase in AD performance. We thus provide evidence in support of an adolescent development of world knowledge-based AD over and above development of EF.

When participating in dialogue, speakers design their utterances to accommodate the individual needs of listeners (Bentz, et al., in prep). This feature is known as audience design (Clark & Murphy, 1982). Although audience design is central to conventional conversation, it is not known at which age speakers begin taking into account the world knowledge/frame of reference of their interlocutors. Indications from recent studies suggest that albeit preschool and first grade children engage in basic forms of perspective taking (Nadig & Sedivy, 2002), they fail to adapt their utterances in accordance with listener-specific needs in reference production (Pagmar, et al., in prep). Adult participants do however adapt their utterances, and individual differences in the adult population were not dependent on cognitive control function (Bentz, et al., in prep). The dependence on cognitive control function, e.g. switching, may be hypothesized to be greater in children. The current study aims to test the referential production of two age groups; early and mid adolescents (11;0-12;11 and 15;0-16;11), with the purpose of tracing the development of the ability to use information regarding listener-perspective during on-line referential production, and test its relation to cognitive control. The paradigm builds further on the well-established Director’s task but does not require the participants to take the visual perspective of the listener. Instead, participants are presented with a set of pictures portraying referents well-known to them, e.g. popular cartoon characters, hosts of children’s tv-shows, etc. Knowledge of the referents are controlled through post-test surveys. Furthermore, they are asked to direct listeners of two distinct groups, small children and elders, into choosing the target referent. Participants who take the frame of reference of addressees into consideration are expected to adopt different strategies when addressing the different groups, i.e., increase informativeness when denoting referents assumed to be unknown to the listener vs using less informative referential expressions (such as proper names) when denoting referents judged to be known to the listener. Cognitive control/executive function is assessed using the Wisconsin card sorting task. Results are discussed in terms of cognitive costs of switching strategies and the Gricean maxim of quantity.

The purpose of the present study was to introduce a computational simulation of timing in child-adult interaction. The simulation uses temporal information from real adult-child interactions as default temporal behavior of two simulated agents. Dependencies between the agents’ behavior are added, and how the simulated interactions compare to real interaction data as a result is investigated. In the present study, the real data consisted of transcriptions of a mother interacting with her 12- month-old child, and the data simulated was vocalizations. The first experiment shows that although the two agents generate vocalizations according to the temporal characteristics of the interlocutors in the real data, simulated interaction with no contingencies between the two agents’ behavior differs from real interaction data. In the second experiment, a contingency was introduced to the simulation: the likelihood that the adult agent initiated a vocalization if the child agent was already vocalizing. Overall, the simulated data is more similar to the real interaction data when the adult agent is less likely to start speaking while the child agent vocalizes. The results are in line with previous studies on turn-taking in parent-child interaction at comparable ages. This illustrates that computational simulations are useful tools when investigating parent-child interactions.

A language user must rely on several different abilities to carry out a conversation, e.g. the ability to acknowledge the conversational contributions of others, to respond appropriately, to stay on topic, etc. There are many aspects of the development of conversational conduct that are yet unknown. In this study, the longitudinal development of conversational conduct, as in acknowledging one’s interlocutor’s previous turn, were traced from age 5;0 to 7;2. We also investigated whether conversational conduct was predicted by core language skill, executive functions, and specific pragmatic abilities. Previous findings of productive morpho- syntactic accuracy were replicated, while findings concerning longitudinal receptive vocabulary were not. We also found connections between childrens’ conversational responses and executive functions, working memory, and the comprehension of conversational implicatures. The results suggest that conversational conduct is dependent on both inferring communicative intentions, as well as being able to keep track of others' contributions and how they relate to previous turns.

Previous research has shown longitudinal connections between children’s growth rate of observed number of word types in spontaneous production and later language abilities. It is unknown whether this relationship also can be identified through parental reports representing the productive vocabulary. Using longitudinal parental reports (N=64), we examined the predictive value of size, velocity, and acceleration of the parental reported assessments of the productive vocabulary for measures of later core language ability (measures of receptive vocabulary and productive grammar), and later measures tracking language use and pragmatic skill (measures of conversational conduct and the comprehension of conversational implicatures). For a small subset of our sample, we also examined the relationship between parental reported assessment of productive vocabulary and observed number of word types in spontaneous production at the same ages, at four different occasions. Results show that growth rates from parental reports of productive vocabulary inform later language ability, but not to the same extent as in previous research. One suggested explanation for this finding is differences between measures representing vocabulary. No connections were found between early assessment of the productive vocabulary and later language use/pragmatic skill, which is in agreement with one of two suggested outcomes, indicating that the early state of the lexicon is not informative for the included measures of later language use. Lastly, as expected, we found high correlation coefficients between assessment of productive vocabulary and number of word types in spontaneous production, which can be explained by the vast variance in lexical access during early development rather than the accuracy of the included measures.