Abstract
Various stimulus attributes (e.g., the size of visual field) have been examined by previous vection (illusory self-motion perception) studies. However, the number of the stimulus components has not been focused on ever. The present study investigated whether the objective/subjective number (differentiated by Gestalt-law) could influence vection. In Experiment 1, we presented 8 movies consisting of different number (1, 2, 3, 4, 8, 16, 64, 256) of white circles. The total amount of the size of the visual filed occupied by those dots was always constant. The stimulus always moved rightward horizontally, and each movie lasted for 30 seconds. 12 participants were required to press the button if they were perceiving vection and rated the subjective vection strength by using a 101-point rating scale. The results showed that the physical (objective) number of circles had a significant positive impact on vection strength even though the total area of the stimuli was constant. In Experiment 2, we presented 3 movies consisting of two orange circles or one single white oval or two orange circles closed by the white oval. Relating to the closure principle, the bigger white oval can reduce the subjective stimulus number, we assumed. In Experiment 3, relating to the proximity principle, we presented 3 movies consisting of 12 black circles with every 4 arranged closely, or every 4 closed by 3 blue quadrangles relatively, or just 3 blue quadrangles. In Experiment 4, relating to the similarity principle, we presented 4 movies consisting of 16 circles grouped together under the same/randomized color (black/red/green/orange), and 16 drawings under the same/randomized shape (circle/triangle/rounded rectangle/pentagon). There was no clear and simple significant effect of Gestalt principles on vection strength. The effect of the objective/subjective number of stimuli on vection should be examined more in the future.