Do young children acquire the meaning of to know and to believe simultaneously or not?
The conceptual meaning and linguistic use of to know are usually considered to occur earlier than those of to believe. However, the data supporting this claim do not take into account some sources of variation: The difference in the assessment between comprehension and production and the link established between action and representation in standard tasks like that of Wimmer and Perner(1983). The authors counter this claim and attempt to demonstrate a developmental parallelism between the two epistemic operators to know and to believe. This parallelism would be due to the absence of a link between belief and action in a first phase, both developing in a modular system but linked to implicit or explicit access to information, contrary to the usual conception in the literature. Three experiments are reported. The first and the second showed an equal difficulty level between to know and to believe in comprehension in both a declarative and a procedural false belief task and, to the contrary, a lag between the comprehension of to believe and the prediction of a declaration or an action based on a false belief. The third demonstrated that earlier success in attributing a false belief to the other was not a false positive.