Reliability and generalizability of an acted-out false belief task in 3-year-olds.

The current study tested the reliability and generalizability of a narrative act-out false belief task held to reveal Theory of Mind (ToM) competence at 3 years of age, before children pass verbal standard false belief tasks (the "Duplo task"; Rubio-Fernández & Geurts, 2013, Psychological Science). We conducted the task across two labs with methodologically improved matched control conditions. Further, we administered an analogue intensionality version to assess the scope of ToM competence in the Duplo task. 72 3-year-olds participated in a Duplo change-of-location task, a Duplo intensionality task, and half of them in a matched verbal standard change-of-location task, receiving either false belief or matched true belief scenarios. Children performed at chance in the false belief Duplo location change and intensionality tasks as well as in the standard false belief task. There were no differences to the standard task, and performance correlated across all three false belief tasks, revealing a rather unified competence and no task advantage. In the true belief conditions of both Duplo tasks, children performed at ceiling and significantly different from the false belief conditions, while they were at chance in the true belief condition of the standard task. The latter indicates that a pragmatic advantage of the Duplo task compared to the standard task holds only for the true belief scenarios. Our study shows that the Duplo task measures the same ToM competence as the standard task and rejects a notion of earlier false belief understanding on the group level in 3-year-old children.