Beyond false belief understanding: Theory of Mind development in infancy 

Jessica Yott, Ph.D.
Concordia University, 2015

Theory of Mind (ToM) development in infancy has generally been investigated using studies conducted on a single age group with a single task, usually measuring false belief. The goals of the current dissertation were to examine ToM understanding in infancy using multiple tasks, two paradigms, and a within-subjects design. An additional goal was to determine if ToM abilities in infancy follow a predictable pattern of development. 
The aim of the first study was to investigate 14- and 18-month-olds’ understanding of intentions, true beliefs, desires, and false beliefs using a violation of expectation paradigm. To do so, Study 1 used a within-subjects design, whereby infants observed both a congruent and an incongruent trial for each task. Results revealed that both groups of infants looked significantly longer at the incongruent trial on the intention and true belief tasks. In contrast, only 18-month-olds looked significantly longer at the incongruent trial of the desire task. Lastly, neither age group looked significantly longer at the incongruent trial of the false belief task. Furthermore, inter-task analyses revealed only a significant correlation between looking time at the false belief and intention tasks.
The second study examined if ToM abilities developed in a predictable sequence as observed in preschool children. To do this, 18-, 24-, and 30-month-olds completed four tasks measuring intention, emotion, desire, and false belief understanding, using interactive spontaneous-response tasks. Results revealed that infants’ ToM understanding does develop in a predictable scale sequence. That is, infants were more likely to pass the intention task, followed by the emotion, desire, and false belief task. Moreover, infants’ performance on the intention, emotion, and false belief tasks appeared to improve with age.
Together, the results from both studies suggest that ToM abilities begin to develop in infancy. However, results from the current dissertation also highlight some of the limitations in infants’ ability to reason about other people’s mental states. Nevertheless, using two distinct paradigms, the present findings demonstrate that intention, emotion, and true belief understanding develop before more complex ToM abilities, including desire and false belief understanding. Furthermore, these results suggest that implicit ToM follows a similar developmental sequence as observed in more explicit ToM development.