Poor peripheral binding depends in part on stimulus color

The Distinctness of Illusory and Non-Illusory Conjunctions in the Perception of Chinese Words: Assessing the Roles of Stimulus Exposure Time

Previous studies of illusory conjunction (IC) mainly focused on alphabetic languages, while researchers have poorly understood the IC mechanism of Chinese words as an ideographic writing system. In the present study, we aimed to investigate the dynamic changes of IC effects for Chinese words under different stimulus exposure times and spatial arrangements. We conducted two experiments with a 3 (Condition: IC, non-IC-same, non-IC-different) × 3 (Exposure time: 38 ms, 88 ms, 138 ms) within-subject design. The results showed that in the IC condition, the two characters recombined regardless of exposure time as long as they could form an orthographically correct new word, demonstrating the universality of IC. In non-IC conditions, increasing exposure time decreased response time and significantly reduced error rate, indicating that attention played a decisive role in perceptual processing. The spatial arrangement had no impact on IC production. These findings support the feature confirmation account model, suggesting that attention modulates IC through top-down feature confirmation processes. These data expand an understanding of IC mechanisms, validate the role of attention in feature confirmation, and elucidate the inimitable mechanism of the Chinese word IC influenced by both low-level visual processing and high-level cognitive control.

Central-peripheral dichotomy: color-motion and luminance-motion binding show stronger top-down feedback in central vision

Recently a theory (Zhaoping, Vision Research, 136, 32-49, 2017) proposed that top-down feedback from higher to lower visual cortical areas, to aid visual recognition, is stronger in the central than in the peripheral visual fields. Since top-down feedback helps feature binding, a critical visual recognition process, this theory predicts that insufficient feedback in the periphery should make feature misbinding more likely. To test this prediction, this study assessed binding between color and motion features, or between luminance and motion features, at different visual field eccentricities. We first used color-motion stimuli containing equiluminant red and green dots moving in opposite directions, for example, red dots moved leftward while green dots moved rightward. Such stimuli were shown in both a central reference strip and a peripheral test strip; participants reported whether it was the first or second interval in a trial in which the dots of each color moved in the opposite directions between the two strips. The center of the test strip was at 4° or 15° away from the gaze fixation. Participants' performance was much worse when the test strip was more peripheral, suggesting that feature misbinding occurred more frequently there. This held even when the size and density of the dots were adjusted by eccentricity-dependent cortical magnification factors, and even when red/green dots were replaced by yellow/blue dots or black/white dots to suit the retinal input sampling peripherally. Our findings support that top-down feedback is more directed to central vision, which can resolve ambiguities in feature binding at more central visual locations.