Shared mechanisms underlie some but not all motion-position illusions.

Cottier, T., Turner, W., Holcombe, A., & Hogendoorn, H.

This website provides videos of the motion-position illusions we used. For more information about the Time in Brain and Behaviour Laboratory, please visit the lab’s website: timinglab.org.

Flash-drag effect (FD)

Explanation: Two vertically aligned lines are flashed alongside moving gratings. However, these lines are perceived unaligned, as their perceived positions are displaced in the direction of their closest grating’s motion. The right grating is always moving in the opposite direction to the left grating. When the right grating is moving upwards, the left grating will be moving downwards, so you should perceive the right line to be above the left line. When the right grating is moving downwards, you would expect the opposite.

Whitney, D., & Cavanagh, P. (2000). Motion distorts visual space: shifting the perceived position of remote stationary objects. Nature Neuroscience, 3, 954–959. https://doi.org/10.1038/78878

Flash-grab effect (FG)

Explanation: An annulus rotates clockwise for 900ms then reverses direction, rotating counterclockwise for 500ms. At the time of the reversal, a red circle is presented in the bottom centre of the annulus. This circle is perceived to be grabbed in the reversal direction. In this example the annulus reverses counterclockwise, therefore, the red circle will be perceived offset right from the centre.

Cavanagh, P., & Anstis, S. (2013). The flash grab effect. Vision Research, 91, 8–20. https://doi.org/10.1016/j.visres.2013.07.007

Flash-lag effect (FLE)

Explanation: There is a rod rotating clockwise. When the rod reaches zero degrees, a stationary flash is presented in spatio-temporal alignment with this moving rod. While the flash and rod are aligned, the rotating rod is perceived in a position further along its motion trajectory, with the flash lagging behind.

Nijhawan, R. (1994). Motion extrapolation in catching. Nature, 370, 256–257. https://doi.org/10.1038/370256b0

Luminance flash-lag effect (LUM-FLE)

Target’s luminance is becoming darker

Target’s luminance is becoming brighter

Explanation: There is a target circle either above or below the fixation dot continuously changing in luminance (becoming brighter or darker). At a point in time, a circle with fixed luminance is flashed on the other side of the fixation dot. When the flash is presented, the flashed circle and target circle have the same luminance. Yet, the changing target circle will always be perceived with a luminance value further along its luminance ramp. For example, at the time of the flash, if the target is becoming darker, then the target will be perceived as darker than the flash even though their luminance is identical.

Sheth, B. R., Nijhawan, R., & Shimojo, S. (2000). Changing objects lead briefly flashed ones. Nature Neuroscience, 3(5), 489–495. https://doi.org/10.1038/74865

Fröhlich effect (FE)

Explanation: In this example, the rod always starts positioned in the centre of the screen pointing straight upwards. Motion biases the starting position of the rod in its direction of motion, so the rod is perceived to start in a clockwise position further along its motion trajectory.

Fröhlich, F.W. (1924). Über die Messung der Empfindungszeit. Pflügers Arch, 202, 566–572. https://doi.org/10.1007/BF01723521

Motion induced position shift (MIPS)

Explanation: There are four stationary gabors with phase modulated gratings. The top and bottom gabors were always horizontally aligned, but the bottom gabor’s gratings always moved in the opposite direction of the top gabor’s. Motion biases the object’s position, so the gabors are perceived in a position in the direction their grating’s rotate. In this example, the top gabors should be perceived in a position to the right of the bottom gabors.

De Valois, R. L., & De Valois, K. K. (1991). Vernier acuity with stationary moving Gabors. Vision Research, 31(9), 1619–1626. https://doi.org/10.1016/0042-6989(91)90138-U

Twinkle-goes illusion (TG)

Static background noise

Dynamic background noise

Nakayama, R., & Holcombe, A. (2021). A dynamic noise background reveals perceptual motion extrapolation: The twinkle-goes illusion. Journal of Vision, 21(11):14, 1-14. https://doi.org/10.1167/jov.21.11.14

Explanation: The two squares always disappear when they are vertically aligned. When the background noise is static when the squares disappear, the squares’ final position should appear vertically aligned. When the background noise is dynamic, the squares’ final positions should appear displaced in their direction of motion.

Flash-jump effect (FJ)

Top bar is shrinking in height, while the bottom bar is growing in height

Top bar is growing in height, while the bottom bar is shrinking

Explanation: Two bars are moving towards each other while their height changes. The bottom bar changes height in the opposite direction to the top bar. When the bars are vertically aligned, their height is identical and they briefly flash white. However, this white flash is perceived on a bar further along the bar’s motion and height trajectory. To clarify, if the bar is moving left to right and increasing in height, at the time of the flash, the flash won’t be perceived in the centre, but will be perceived on a taller bar in a position right of centre.

Cai, R., & Schlag, J. (2001). A new form of illusory conjunction between color and shape. Journal of Vision, 1(3), 127–127. https://doi.org/10.1167/1.3.127