Thus, the younger children did not generally turn the glasses less precisely. The effect of diameter,
therefore, did not fail to reach statistical significance because of higher error variance. It is more likely
that the younger children in fact considered the glass diameter to a lesser extent. In combination with
the results of Experiment 1, where the glass diameter was considered when the glasses were tilted
manually, it can be concluded that actively executed actions are of central importance and have a beneficial
effect on younger children’s mental transformations. Even at 7 years of age, performance was
not quite as good in the remote control task as with hands-on manual tilting. However, with increasing
age, transforming mental representations becomes increasingly independent from motor activity.