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Visual Motion Integration


I have been working on the Rubber Pencil Illusion (Thaler, L., Todd, J.T., Spering, M., & Gegenfurtner, K.R. (2007). Illusory Bending of a rigidly moving Line Segment: Effects of Image Motion and smooth pursuit Eye Movements.Journal of Vision, 7(6), 1-13. [link to free article]).
Below you can see animations that illustrate (i.e. not replicate) some of the motion displays used in the experiments. All animations are flash files and Macromedia flash player is required to view them. If you do not have the flash player you can download it here.

All displays show a rigidly moving line segment. However, in some displays observers perceive (illusory) bending motion.
The animations should be viewed on a CRT at 75 Hz. If you view them on 'sluggish' displays, i.e. LCD displays that have long persistency, image quality will be compromised and you may not perceive bending motion. I found, that the animations play slowly when you you look at them in your browser. I recommend that you download (right-click on the links provided and then save) and open them in flash.

Demo 1a   Download here.
shows a line segment in pure translatory motion. Observers commonly perceive this motion as rigid.

Demo 1c   Download here.
shows a line segment in a combination of rotational and translatory motion. Observers commonly perceive this motion as non-rigid, or bending.

Demo 1e   Download here.
shows a line segment in translatory motion (as in Demo 1a). In addition, the line segment rotates around the center of the display at constant velocity. Observers commonly perceive this motion as rigid.

Demo 1g   Download here.
shows a line segment in a combination of translatory and rotational motion (as in Demo 1c). In addition, the line segment rotates around the center of the display at constant velocity. Observers commonly perceive this motion as non-rigid, or bending.

Demo 4   Download here.
shows a line segment in a combination of translatory and rotational motion (as in Demo 1c). In addition, a rectangle moves in-phase with the line segment. Observers commonly perceive this motion as more rigid than the line segment alone (compare Demo 1c), but less rigid than pure translatory motion (compare Demo 1a).

Here are two other demos that show elliptical contours in motion.
Please see Yair Weiss & Edward Adelson's paper
on more information on these stimuli.

Demo 5   Download here.
shows an elliptical contour in motion. Observers commonly perceive the ellipse as non-rigidly deforming.

Demo 6   Download here.
shows an elliptical contour and two points in motion. Observers commonly perceive the ellipse as rigidly rotating. NOTE that the motion of the ellipse is the same in demo 5 and 6!