Haruaki Fukuda

Radial lines of Ehrenstein patterns induce illusory scintillating lustre in gray disks inserted into the central gaps (scintillating-lustre effect). We report a novel variant of this illusion by replacing the radial lines with white and black radial fins. Both white and gray disks inserted into the central gaps were perceived as scintillating, if the ratio of the black/white fin width were balanced (ie, close to 1.0). Thus, the grayness of the central disk is not a prerequisite for the scintillation. However, the scintillation was drastically reduced when the ratio was imbalanced. Furthermore, the optimal ratio depended on the color of the center disks.

We can easily recognize human movements from very limited visual information (biological motion perception). The present study investigated how upper and lower body areas contribute to direction discrimination of a point-light (PL) walker. Observers judged the direction that the PL walker was facing. The walker performed either normal walking or hakobi, a walking style used in traditional Japanese performing arts, in which the amount of the local motion of extremities is much smaller than that in normal walking. Either the upper, lower, or full body of the PL walker was presented. Discrimination performance was found to be better for the lower body than for the upper body. We also found that discrimination performance for the lower body was affected by walking style and/or the amount of local motion signals. Additional eye movement analyses indicated that the observers initially inspected the region corresponding to the upper body, and then the gaze shifted toward the lower body. This held true even when the upper body was absent. We conjectured that the upper body subserved to localize the PL walker and the lower body to discriminate walking direction. We concluded that the upper and lower bodies play different roles in direction discrimination of a PL walker.

We found a novel visual illusion by using a rotating disc that has some coloured sectors with black arcs. When this disc rotates, illusory colours are seen in the concentric rings that are created by the rotating arcs. The illusory colours are the opponent colours of the sectors that the corresponding arcs are in. Even though we could not differentiate the colours of the individual sectors when the disc rotated quickly the illusory colours that were the opponent colours of the sector colours could be seen. This visual illusion thus suggests that our visual system can process visual stimuli that we cannot perceive as colours.