Judgment Biases of Temporal Order during Apparent Self-Motion

Wataru TERAMOTO  Hiroshi WATANABE  Hiroyuki UMEMURA  Katsunori MATSUOKA  Shinichi KITA  

IEICE TRANSACTIONS on Information and Systems   Vol.E87-D   No.6   pp.1466-1476
Publication Date: 2004/06/01
Online ISSN: 
Print ISSN: 0916-8532
Type of Manuscript: Special Section PAPER (Special Section on Human Communication I)
virtual reality,  vection,  temporal order judgment,  perceptual asynchrony,  

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Virtual reality system is one of the most useful tools for investigating the characteristics of human perception in dynamic visual environment because we can easily and appropriately manipulate parameters of three-dimensional stimuli of vision in accordance with our purpose. In the present study we examined how the brain processes local stimuli during the global sensation of self-motion (vection) in view of temporal information processing -- perceptual latency -- with temporal order judgment task. In Experiment 1 we demonstrated that the targets in the left visual field were perceived prior to those in the right visual field when an observer stared at rightward optokinetic stimuli or perceived self-motion leftward, and vice versa. Especially at 16.0 deg of target eccentricity the biases were much larger with the continuous exposure of optokinetic stimuli than with their intermittent exposure; the former compelled observers to perceive self-motion and the latter hardly did. In Experiment 2 we examined the relationship between the occurrence of vection and temporal order judgments as the exposure duration of optokinetic stimuli was fixed between conditions, and showed that the biases were larger when vection occurred than when it did not. In Experiment 3 we showed that the biases were not modulated by the speed of optokinetic stimuli and not related with the speed of perceived self-motion. This phenomenon can be explained based on exogenous components of attention, the shift of the reference frame for determining the order in which objects come into awareness and imbalance between hemispheric activities. The mechanism is ecologically reasonable in that it allows us to be aware of the incoming events as soon as possible and to avoid any dangerous situations.