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Daniel Chen, Richard So; Speed judgments of background motion and illusion of self-motion when viewing sinusoidal visual stimuli along fore-and-aft axis with different frequencies and velocities. Journal of Vision 2014;14(10):1356. doi: 10.1167/14.10.1356.
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© ARVO (1962-2015); The Authors (2016-present)
Motivation: The ability to accurately judge the speeds of background motion is crucial for many daily tasks, such as driving. While viewers who experienced illusion of self-motion (vection) tend to overestimate the speed of a moving object (i.e., positive perceived speed bias (PSB): Gray and Regan, 2000), little is known about the effect of vection on speed perception of a moving visual background. Experiment: In this study, vection was provoked by viewing a wide field-of-view (horizontal: 220° x vertical: 56°) radial checker-board pattern oscillating in sinusoidal motions along the fore-and-aft axis. There were 5x5 full-factorial experimental conditions studying different combinations of RMS velocities (from 11 m/s to 178 m/s) and oscillation frequencies (from 0.05 Hz to 0.8 Hz). Subjects were required to estimate their perceived vection as well as their perceived speeds of the visual background motion using a ratio-scale method with a reference stimulus (0.2 Hz with 44 m/s). Ten subjects completed four repetitions for each condition. Results: In general, perceived vection was not significantly correlated with PSB (Spearman: rho=.017, p=.584). However, when frequencies were lower (below 0.2Hz) or velocities were higher (above 89 m/s), the presence of vection was associated with significantly higher positive PSB (Spearman: rho>.2, p<.01). We also observed that frequency of the stimuli had significant effects on PSB as well as on vection perception which were opposite to the effects of velocity. In short, impacts of frequency and velocity were in opposition. Conclusion: The presence of vection encouraged the viewers to increase their perceived speeds but such effect was modulated by both frequency and velocity of the background motion.
Meeting abstract presented at VSS 2014
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