Effect of head translation and manual control on depth sign perception from motion parallax

[摘要] Motion parallax produced during observer translation acts as a cue for perceiving relative depth. However, when information about observer translation is unavailable, the perceived sign of depth is ambiguous. This is theoretically and empirically ascertained. This study focuses on manual control, in comparison with head translation, as a cue for perceiving depth sign, since action can affect vision. Harman et al. (1999), for instance, reported that human object recognition was better when the observer could rotate the object images using a trackball rather than passive observation. In this study, an experiment was conducted to investigate the effect of manual control on reducing ambiguity of depth sign perception. For comparison, the effect of observer translation was also investigated. Stimuli were generated by a computer and presented on a CRT monitor. Four participants took part in the experiments. The displays simulated a corrugated surface in the frontoparallel plane, and it could be rotated to-and-fro around a vertical axis. In the experiment, each corrugated surface had one of two possible spatial phases (center-far/center-near). The surface structure was depicted with random dots on a black background. The stimulus change was associated with the rotation of a knob manipulated by the participant, or the lateral translation of a chin rest yoked to head translation. The axis of the knob was aligned with the axis of the stimulus rotation. The display was presented during participant manipulation or translation. Participants were forced to discriminate between center-far and center-near. Participants with head translation perceived the depth sign with almost perfect accuracy. Participants with manual control, by contrast, perceived the depth sign with around 0.75 accuracy (chance level 0.5). This suggests that reliability of visual change of outer world from head translation is higher than that from manual control in the visual system.

[学科分类] 眼科学