“…First, they argued that responses to the forced-choice questionnaires may be biased toward the scientific view because the choice between a scientific answer and an intuitive one is limited and because of the lack of justifications of answers. However, empirical evidence with respect to conservation of volume (Kingma, 1984;van der Maas & Molenaar, 1996), the class inclusion task (Chapman & McBride, 1992;Hodkin, 1987;Thomas, 1995;Thomas & Horton, 1997), and the balance scale task (Jansen & van der Maas, 1997, 2002Siegler, 1981) has demonstrated that, if the construction of the test is based on extensive research on possible alternative strategies, it is possible to design a forced-choice task that does not overestimate children's knowledge and allows for the detection of alternative strategies.…”