Probing the depth of infants' theory of mind: disunity in performance across paradigms

There is currently a hot debate in the literature regarding whether or not infants have a true theory of mind (ToM) understanding. According to the mentalistic view, infants possess the same false belief understanding that older children have but their competence is masked by task demands. On the other hand, others have proposed that preverbal infants are incapable of mental state attribution and simply respond to superficial features of the events in spontaneous-responses tasks. In the current study, we aimed to clarify the nature of infants' performance in tasks designed to assess implicit theory of mind (ToM) by adopting a within-subject design that involved testing 18-month-old infants on two batteries of tasks measuring the same four ToM constructs (intention, desire, true belief, and false belief). One battery included tasks based on the violation-of- expectation (VOE) procedure, whereas the other set of tasks was based on the interactive, helping procedure. Replication of the original findings varied across tasks, due to methodological changes and the use of a within-subject design. Convergent validity was examined by comparing performance on VOE and interactive tasks that are considered to be measures of the same theory of mind concept. The results revealed no significant relations between performance on the pairs of tasks for any of the four ToM constructs measured. This pattern of results is discussed in terms of current conflicting accounts of infants' performance on implicit ToM tasks. A video abstract of this article can be viewed at: https://www.youtube.com/watch?v=U3vqfe_zdhA&feature=youtu.be.