Friday, 15 June 2012

Troxler fading

Stare at the red dot in the center of the figure for a minute or two. Before long, the green ring will disappear--it simply seems to fade into the white background. There are no tricks: This is a simple, static image file. The effect has been known for more than two centuries and is named for its discoverer, Ignaz Paul Vital Troxler (1780-1866), a Swiss physician and philosopher. "Troxler fading" is actually related to what you experience when you get "dizzy": You become so habituated to a phenomenon (spinning in a circle or seeing a green ring in your peripheral vision) that you stop noticing it's there.
Or, rather, you don't realize that your perceptual system has begun actively ignoring it. It's only when your circumstances change that you see what the phenomenon has done to your perceptual system. When you stop spinning, the world seems to continue, in reverse. When you look away from the green ring, you see a red ring in the same part of your visual field.  
This is a perceptual illusion but I like to use it to demonstrate that children with CVI can only focus their attention on one thing. The rest of the world does not seem to exist for them while they attend to the one thing. Note that as you blink it comes back in to focus. The CVI child needs to sort of 'blink' to cause other things to stand out. Make of this what you will it; at least will 'give you pause', I hope. 


  1. I recently made an app for android that takes a picture of a page (words) and then speaks it aloud. I wanted to do it open source (free), inspired by a Ted Talk video that stated this technology used to cost a lot.
    Now any android phone can do it, here it is I'm trying to get it out there to those who can use it:

    On the left of the app page you will also see a version that takes a picture of ANY language (but this one is more geared to travelling:)


  2. This is one of the nice experiments. Changing in the thought of working to the crowd can really helpful to fine the new supportive changes.

  3. Above link has been changed, See Say Image to Speech for the Visually Impaired is now here on Google Play:

    Take Picture of Book Page, Android Reads it Aloud! See Say Image to Speech OCR.
    An app for android that takes a picture, and speaks the text aloud:) A tool for the visually impaired, or just for the curious.
    I was inspired by a Ted Talk that mentioned that not too long ago, this technology was available for around $10,000.00, for the visually impaired. Technology has come so far that I am able to write this app and release it for under five bucks :)

  4. There is also one that does page image to speech translating from any language:

  5. Further along the lines of Visual Impairment, I spent the better part of 6 months developing Object Recognition, in other words, picture of ANY object to speech. This tool works best on "things", not people, and it gets smarter each update. It's named ANDROID EYE, and it won Reviewers Choice Award, with much great positive feedback: