Spatial congruency bias in identifying objects is triggered by retinal position congruence: Examination using the Ternus-Pikler illusion

When two different objects are sequentially presented at the same location, the viewer tends to misjudge them as identical (spatial congruency bias). The present study examined whether the spatial congruency bias would involve not only retinotopic but also non-retinotopic processing using the Ternus-Pikler illusion. In the experiments, two objects (central and peripheral) appeared in an initial frame. The target object was presented in the central area of the display, while the peripheral object was either on the left or right side of the target object. In the second frame, the target object was again presented in the central area, and the peripheral object was on the opposite side. Two kinds of inter-stimulus intervals were used. In the no-blank condition, the target object was perceived as stationary, and the peripheral object appeared to move to the opposite side. However, in the long-blank condition, the two objects were perceived to move together. Participants judged whether the target objects in the two frames were identical. As a result, the spatial congruency bias occurred irrespective of the ISI conditions. Our findings suggest that the spatial congruency bias is mainly based on retinotopic processing.