It is possible that the visual information about the glass movement served as a reference frame for
the imagined water inside the glass, thereby helping to smoothly transform the mental representation
of the water. Furthermore, it seems possible that the visible movement of the glass allowed smooth
pursuit movements of the eyes that might have mediated a smooth mental transformation. In the
blind tilting task, on the other hand, without a moving visual cue to hang onto, the eyes might have
jumped in saccades or even stayed fixated.