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Science

It's Surprisingly Hard To Notice When Moving Objects Change 140

Posted by Soulskill
from the sorry-officer-the-traffic-light-was-swinging-in-the-wind dept.
An anonymous reader writes "Scientists at Harvard have found that people are remarkably bad at noticing when moving objects change in brightness, color, size, or shape. In a paper published yesterday (PDF) in Current Biology, the researchers present a new visual illusion that 'causes objects that had once been obviously dynamic to suddenly appear static.' The finding has implications for everything from video game design to the training of pilots."
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It's Surprisingly Hard To Notice When Moving Objects Change

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  • by pz (113803) on Friday January 07, 2011 @07:47PM (#34799082) Journal

    IAAVN (I am a Visual Neuroscientist). It's a compelling illusion. I have not read the original paper, but will speculate nevertheless in true Slashdot fashion. The change that's perceived before the ring rotates is not so much due to the colors changing -- if you pay close attention -- but something that's called apparent motion. The classic example of apparent motion is the sequencing of lights around a movie marquis -- they appear to move, although the lights themselves are not actually moving. In the same way, the static ring has internal apparent motion as the colors change, because your brain is interpreting, for example, one dot turning yellow next to a dot that was previously yellow, as motion of a yellow dot, even though the underlying dots do not move. While apparent motion can be very strong, it is not the same as true motion.

    Then, when the ring starts to rock back and forth, there is a true motion signal that swamps the apparent motion. If you pay attention to a given dot while holding your gaze still fixed at the central white point (not as hard as it sounds), you can clearly still see the colors changing.

    So without having read the paper, I reserve some skepticism that they have not actually measured what they think they have. Change is still perceptible, but it would seem that real motion interferes with apparent motion.

  • Re:I don't see it. (Score:2, Informative)

    by Anonymous Coward on Friday January 07, 2011 @08:08PM (#34799328)

    Follow the link to the youtube video - they have the bandwidth!

  • by JordanL (886154) <jordan@ledoux.gmail@com> on Friday January 07, 2011 @08:55PM (#34799908) Homepage

    You might call it a defect, I might think of it as evolutionary design.

    I call it evolutionary accident through a process of natural selection propagated by random mutations and favorable environmental factors to suppress competing alleles.

  • by Anonymous Coward on Friday January 07, 2011 @09:00PM (#34799984)

    Decepticons have known this trick for aeons....

  • by suchow (1972574) on Friday January 07, 2011 @09:59PM (#34800554)
    hi jon, i'm one of the authors of the paper. just thought i'd answer your question about the refresh rate. we used laptop screens that ran at 60 Hz, but the demo works even if you keep the dots motionless and lift up the screen and rock it back and forth. (you can try this yourself if you download the video.) the demo also works on a CRT at 120 Hz. so yes, it the refresh rate was considered and controlled for, and it doesn't seem to matter much. the motion in the youtube and vimeo videos are a bit jerky because they were converted to 30 fps.
  • Re:News Flash (Score:4, Informative)

    by Z34107 (925136) on Friday January 07, 2011 @10:18PM (#34800680)

    "I can even see color with it" ...is this supposed to be odd or something?

    Yes, because only the cones [wikipedia.org] in the center of your eye are capable of perceiving color (the rods on the outside perceive only black and white.) Your brain senses everything in the periphery of your vision in black and white, but "fills in" best-guess colors from what your cones perceive directly in front of you.

    I remember that from a psychology lecture only because a fellow classmate, like the parent poster, couldn't believe the color in his peripheral vision was an illusion. So, the professor drew an "X" in the middle of the chalkboard and asked him to stare at it without looking away. He then held up a colored note card directly in front of the "X" and asked him to name the color. (Of course, he named it correctly.)

    The professor held up another note card, a bit further away from the X, and asked him to say what color that card was. And then he held up the next card, a bit further away from the X than the last one. And he kept holding the cards further and further towards the edge of his field of vision.

    After about the fifth card, the kid was convinced that any card the professor held up was either a shade of gray, or the same color as the chalkboard. Once the note cards were in his peripheral vision, he couldn't tell what color they were, and couldn't tell that he couldn't tell what color they were. Great professor.

  • by Jesus_666 (702802) on Saturday January 08, 2011 @01:13AM (#34801732)
    That depends on what you call a processor. The eyes do a bit of preprocessing - the raw output of the rods and cones isn't fed directly into the optic nerve; intermediate cells inhibit and excite each other, altering the image in-eye. One example of retinal filtering is how Mach bands [wikipedia.org] are created: Lateral inhibition between the cells causes edges to appear more pronounced than they actually are. The brain is not involved.

    (Essentially, the more light one cell receives, the more its neighboring cells are inhibited. At an edge between a light and a dark area, a "light" cell close to the edge will receive less inhibition than entirely bright-surrounded cells due to its "dark" neighbors and thus the light side of the edge will be perceived as brighter. Conversely, the "dark" cells closest to the edge will receive stronger inhibition than other "dark" cells due to their "bright" neighbors, causing that side of the edge to appear darker.)
  • Re:News Flash (Score:5, Informative)

    by NeutronCowboy (896098) on Saturday January 08, 2011 @05:56AM (#34802692)

    Uh, did you read the Wikipedia link you posted? "Cone cells are densely packed in the fovea, but gradually become sparser towards the periphery of the retina." They aren't located only in the fovea, but all across the retina. They're merely more densely packed in the fovea than towards the edge. What most likely happened to your classmate is cone bleaching [ucsd.edu]: the longer you stare at a particular image, the more the particular cones bleach their photoreceptors, and the harder it is to figure out the correct color. Depending on what color the chalkboard was, it's quite possible he simply had stared at it for too long.

    The retina still perceives color at the edges, it just does so less effectively than if you focus on the center.

I bet the human brain is a kludge. -- Marvin Minsky

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