Spatial and temporal dependencies of the motion bridging effect: Investigations of an illusory motion

Abstract

The Motion Bridging Effect (MBE) is a visual illusion in which a motion that is not consciously visible creates a visible illusionary movement in a preceding or succeeding stationary ring of points. In the initial MBE study (Mattler & Fendrich, 2010), a ring of 16 points (the inducing ring) was rotated at an angular velocity of up to 2250°/s which entails that the point positions on the circumference of the ring were refreshed at temporal frequencies of up to 100 Hz. The observers only saw an uninterrupted outline circle and were unableto judge the rotation direction of the inducing ring. However, when the inducing ring was replaced by a ring of 16 stationary points (the test ring), the stationary ring seemed to visibly rotate to a standstill, mainly in the same direction as the inducing ring was rotating. This demonstrates that although the inducing ring rotation was not consciously perceived, its motion was processed by the visual system. Similar results were found when the test ring preceded the inducing ring: The test ring seemed to accelerate in this case. In this thesis the contributions of temporal frequency, retinal eccentricity, the separation between the points of the test ring, and the inducing ring start and stop position are discussed as mediators of the effect. Furthermore, it is considered that the illusionary movement in the MBE is caused by a new kind of apparent motion, the ring rotation illusion (RRI), whose spatialand temporal dependencies and differences to the MBE are demonstrated. Finally, it is shown that the MBE, which in all previous studies was only demonstrated on an analog oscilloscope, can also be reliably found with an LCD monitor.