Fig. 1: Schematic illustrations of procedure, stimuli, and experimental settings.

A A schematic illustration of a single trial in Experiments 1, 2, 3, and 4. B Schematics of the motion stimuli and the background. The light dots represent the signal dots moving downward under natural gravity. These dots show an acceleration of 1 g in the virtual scene coordinates with the same initial velocity at the upper side of the square. The hollow dots represent the noise dots, which have the same motion parameters as the signal dots except for moving in random directions. We informed the participants that the perspective drawing presented a long tunnel, and the two figures were 1.8 m in height. C Experimental settings of Experiment 5, in which the participants sat 7 m away from a 1.9-m-height projection screen, and the motion stimuli were projected onto the screen without the perspective drawing background.