The effect of eccentricity and spatiotemporal energy on motion silencing
Motion silencing research at LIVE is being conducted in collaboration with CPS (http://www.utexas.edu/cola/cps/).
Introduction
The salient changes of objects in luminance, color, size, or shape may appear to reduce or to cease altogether when the objects move rapidly and collectively (Suchow & Alvarez, 2011). In that study, one hundred small dots were randomly arranged in a ring-shaped pattern around a central fixation mark (the illusion may be viewed at http://visionlab.harvard.edu/silencing/.) When the dots are stationary, continuous changes over time in luminance, color, size, or shape are obviously noticeable; however, when the dots are suddenly sent into continuous rotational motion, the changes become imperceptible. This motion-induced failure to detect change, known as motion silencing, shows that motion can disrupt the perception of changes in visual objects.
Motion silencing clearly depends on the velocity of motion (Suchow & Alvarez, 2011), and it has since been shown that motion silencing also depends on dot spacing in a manner consistent with crowding (Turi & Burr, 2013) and on flicker frequency combined with motion and dot spacing (Choi, Bovik, & Cormack, 2014). Turi and Burr (2013) proposed that the combination of global motion and crowding results in motion silencing and presented evidence that silencing depends on target-flanker spacing with a critical spacing of about half eccentricity, consistent with Bouma's law (Bouma, 1970) and on contrast-polarity. Choi et al. (2014) suggested that a spatiotemporal filter-based flicker detector model can explain motion silencing as a function of stimulus velocity, flicker frequency, and spacing between dots. Peirce (2013) examined whether the awareness of motion signals can be silenced by coherent changes in color or size and whether coherence was a necessary component of motion silencing. His results suggest that neither motion nor grouping is required to induce silencing and that silencing can be generated from other significant visual changes (Peirce, 2013).
Although these studies have substantially contributed to our understanding of what factors contribute to motion silencing, the effect of eccentricity on motion silencing has not yet been extensively studied. Since silencing is largely a peripheral effect, the role of eccentricity is highly relevant. Thus far, eccentricity has only been used in a subsidiary manner, e.g., to scatter random dots over a limited ranges of eccentricities (from 5º to 8º in Suchow and Alvarez, 2011), to measure critical spacing in crowding experiments (at 3.5º and 7º in Turi and Burr, 2013), or to circularly distribute dots at a specific eccentricity (6.42º in Choi et al., 2014). Understanding the effect of eccentricity on motion silencing is important for making the connection between the awareness of object appearance and motion in peripheral vision. Given the large changes in receptive field characteristics with eccentricity, we felt that parametrically varying them might reveal something about the mechanism underlying silencing.
Example Stimuli
We highly recommend viewers to download video stimuli and display them on your PC at 1920 × 1080 resolution at 120 Hz refresh rate monitor with viewing distance 57cm to watch the exact stimuli. (Video stimuli is 120 frame per second. Web rendering can be different from the original stimuli or choppy according to your PC setup. We recommend high performance graphics card, monitor, and solid-state drive(SSD) for smooth presentation of stimuli.)
Download: (S1_ecc4rv20, S2_ecc7rv100, S3_ecc10rv20, S4_ecc10rv160, S5_ecc14rv20), and S6_ecc14rv200).
Instructions: Play the video while looking at the red central fixation mark of the ring. In reality, dots on one of the four rings are changing luminance the entire time; However, the changes are differently noticeable according to motion velocity and eccentricity. Compare the level of silencing between videos: in stimuli S4 and S6, the changes may be imperceptible.
- S1: Eccentricity = 4°, Velocity = 20 angular degree/s
- S2: Eccentricity = 7°, Velocity = 100 angular degree/s
- S3: Eccentricity = 10°, Velocity = 20 angular degree/s
- S4: Eccentricity = 10°, Velocity = 160 angular degree/s
- S5: Eccentricity = 14°, Velocity = 20 angular degree/s
- S6: Eccentricity = 14°, Velocity = 200 angular degree/s
Relevant publication
L. K. Choi, A. C. Bovik,and L. K. Cormack, "The effect of eccentricity and spatiotemporal energy on motion silencing," Journal of Vision., vol. 16, no. 5, pp. 1-13, Mar. 2016. (PDF)