Abstract
Effortlessly tracking the flight of a red frisbee belies the “binding problem,” a challenge the visual system faces integrating multiple features processed along relatively independent neural pathways. Limitations of the binding process are revealed by feature misbinding of color and motion in the periphery of the visual field: With vertical motion of two differently colored groups of dots and each group moving upward or downward, an incorrect (illusory) conjunction of features can be induced so that, say, red dots moving physically upward are perceived to move downward (Wu, Kanai, & Shimojo, 2004). Aim: We investigated if color-motion feature misbinding observed with vertical motion extends to optic-flow motion, which differs by being an ensemble motion percept with continuous motion vectors from center to periphery. Method: Observers saw overlaid groups of moving red and green dots and reported the motion direction of the peripheral dots of one color while fixating at the center. The motion direction assigned to each set of colored dots could be reversed between the center and the periphery to induce misbinding of color and motion. The motion could be vertical, with upwards or downwards direction, or in radial optic-flow, with expanding or contracting directions. Overall, the red and green dots could vary in motion direction, motion type (vertical or optic-flow), or speed. Results/Conclusion: Radial optic-flow motion revealed color-motion feature misbinding in the periphery, as found previously for vertical motion. Mixing motion types (vertical motion for one color and radial optic-flow motion for the other) reduced misbinding by at least 50%. Mixing different speeds caused a smaller but still significant reduction in misbinding. In sum, peripheral feature misbinding of color and motion that results from grouping moving objects in the center and periphery depends on a common motion type and motion speed in the central and peripheral areas.