Stimulus dependencies of an illusory motion: Investigations of the Motion Bridging Effect

[jinglescode]

Paper

Link: https://jov.arvojournals.org/article.aspx?articleid=2734179
Year: 2019

Summary

• using ring of points, check retinal eccentricity with various configurations

Learnings

• Mattler and Fendrich (2007) employed a ring of points that rotated so rapidly observers saw only a fused static ring, but viewing this ring primed direction judgments when observers subsequently viewed a visibly rotating ring
• In 2010 Mattler and Fendrich extended their observations by reporting that viewing such a rapidly rotating ring can produce an illusory rotation in the same direction as the invisible rapid rotation
• increase in the rotation rate increases not only the linear velocity of the inducing ring but also the temporal frequency at which points cross a given position along the circumference of that ring
• Due to limitations in the rate at which the human visual system can track luminance changes, objects that stimulate retinal locations at high temporal frequencies may be perceived as static forms
• temporal frequency at which a flickering light is perceived as steady is termed critical flicker frequency (CFF). While the CFF is influenced by a number of stimulus conditions, including the luminance, size, chromaticity, and sharpness of the test patch, as well as variables such as an observer's light adaptation level
• sensitivity function remains similar in shape but shifts to a lower spatial frequency as the grating is presented at higher velocities, and notes that at velocities greater than 100°/s there is probably no spatial frequency within the range of normal human vision that would allow a grating to have a detectable contrast
• They found that gratings with velocities as high as 800°/s could be detected when the spatial frequency was lowered to 0.01 c/°. They proposed that the limiting factor of motion detection, as is the case with flicker perception, is the temporal frequency of intensity modulations. In their experiment this frequency was approximately 30 Hz. Above this critical rate, motion could no longer be perceived.

Methods

• Participants reported the direction of any perceived rotation (clockwise or counterclockwise)
• Participants were instructed to maintain their gaze on a central fixation point

Results

• conscious perception of motion in the inducing ring only conditions and the MBE in the inducing ring + test ring conditions were dependent on the number of points that formed the rings. Increasing the number of points reduced an observer's ability to discriminate the inducing ring's rotation direction. increasing the point number acted to increase the temporal frequency without altering velocity, the effect of point number is consistent with the premise that the conscious perception of motion was limited by the temporal frequency of the point presentations along the inducing ring circumference
• Changing the diameter of the inducing ring has two major effects: It changes both the retinal eccentricity of the points that form the ring and changes their linear velocity as the ring rotates
• larger ring diameter producing a stronger MBE
• Increasing the diameter of the rings both increased the retinal eccentricity of the points that formed the rings and increased the linear velocity of the points as the inducing ring rotated
• increases in the temporal frequency of activations on the inducing ring circumference might be a critical determinant of the MBE's decline with increasing angular velocity