Abstract
This thesis represents three distinct studies that comprehensively explore how environmental factors contribute to mental-state acquisition in early childhood. Study 1 was a between-subjects longitudinal investigation of 54 infants and 56 toddlers’ statistical pattern learning abilities on a novel ball dispensing task, across four time-points that were spaced three months apart. This study also examined the relationship between toddlers’ statistical pattern learning and their concurrent and subsequent mental-state acquisition, indexed by their mental-state vocabulary and performance on the Diverse-Desires and Diverse-Beliefs ToM tasks using within and between time-point (cross-lagged) correlations. Studies 2 and 3 dissected the impact of parental input on children's ToM understanding. Study 2 employed a within-subjects longitudinal design, encompassing 48 parents and their children (18- to 26-month-olds). Participants interacted over a series of social games in co-view (face-to-face) and digital contexts exploring how parents’ quality of input (initiated, connected, or failed conversations with their child) influenced their talk content (mental-state versus non-mental state), as well as how talk quality and content longitudinally related to their children’s mental state vocabulary. Study 3 employed a between-subjects design, involving a cross-sectional examination of mothers’ talk towards their own toddler or an unfamiliar toddler while mothers described a series of pictures to children. The objective of this study was to understand the nuanced features of parental scaffolding, how parents might talk differently to their own child versus a child with whom they have no prior history, how parental interactions with their children related to their child’s mental-state vocabulary, as well as how parental mood states influenced the dynamics of parent-child communication.
Collectively, the results derived from the triad of studies highlighted the profound impact of the environment on infants’ and toddlers’ learning of mental states, yielding five pivotal insights: 1) Toddlers demonstrated an enhanced ability to discern statistical patterns compared to their infant counterparts, potentially attributable to the advanced development of their selective attention and attentional control, 2) Toddlers’ statistical learning abilities correlated with their subsequent ToM task performance; however, the variability in their ability to detect statistical patterns over the four timepoints suggested that factors like attention and interest may have impacted their learning outcomes, 3) Mothers used more mental state talk in co-view (face-to-face) interactions compared to digital interactions, arguably as face-to-face engagement offered rich non-verbal cues and social relevance. Conversely, digital contexts could have been limited by the video deficit effect, perceptual impoverishment, and delays in feedback between the interactional partners, 4) Parents’ failed talk contained a higher number of mental-state references compared to other types of talk quality, and was a unique and significant predictor of children’s subsequent mental-state vocabulary, emphasising that even disjointed conversations contribute positively to children's evolving ability to mentalise, 5) Mothers engaged with and scaffolded their own child more by using sophisticated mental-state talk about cognitions with them, compared to the unfamiliar child. I argued that this finding was likely attributable to the relationship history that enhanced mothers’ comprehension of their own child's vocabulary so they could offer more effective contingency support.
Overall, the insights gleaned from this thesis highlight the importance of environmental factors on children's comprehension of mental states, providing compelling evidence in favour of the minimalist interpretation of ToM development in infants and toddlers. These findings provide actionable implications tailored to the child's environment, placing an emphasis on parents in implementing positive changes for their children’s social development.