Visual Persistence Survey
Funded by
The Snakes and Ladders Charitable Trust

 
 

People vary in their ability to read text. There may be many contributing causes for this variation. Here we are focusing on one possible cause - interpersonal variations in 'visual persistence'. What is Visual Persistence?

 
  If we are exposed briefly to an isolated visual image (a letter of the alphabet for example), the image of the letter persists in our visual system for a period of around 40 - 250 milliseconds after the stimulus is removed from view. If presented with a rapid sequence of images (such as when reading or tracking movement) a backlog can build up resulting in multiple images persisting simultaneously. The brain resolves this conflict by paying more attention to some of the conflicting images and ignoring or delaying the perception of others. This phenomenon is called 'masking' and can result in a range of perceptual distortions - letters appearing to move about or change position, reversals, parts of words or letters missing, etc.

 
 

In a small initial survey, we found that fast / fluent readers were all at the low (fast) end of the visual persistence scale and that all our 'dyslexic' students have a long visual persistence near the high end of this natural range. We are interested to find out how individual visual persistence correlates to self-assessed reading ability in the adult population.

To take part in the survey - just take this quick test below, click on the 'Start' button and move the slider to the left to increase the speed of the display of characters. Make of note of the fastest speed at which you can comfortably see ALL the letters. Then increase the speed of the display and IF you start to experience visual distortions, make a note of the speed at which this starts to occur. You may experience this as some letters appearing to be grey whilst others are dark and bold.

If you are happy to send us your results then you can use this emailable 'survey response form'.

(If you use a web-based e-mail system you may have to do some cutting and pasting - sorry)

Thanks for taking part.

 
 

The test is written in javascript and runs within your browser, so it poses no threat to you system. You will not be able to see the start button if your computer has active x controls or javascript disabled.

 
 
   

For background references I suggest you start by searching Google Scholar for - 'visual persistence' - 'visual masking' - or go to

J Exp Psychol Hum Percept Perform. 1983 Dec;9(6):923-35 Two tasks involved visual backward masking; the other two were temporal integration tasks. The backward-masking tasks yielded evidence of slower rates of visual information processing in dyslexic children; the temporal-integration tasks yielded evidence of longer duration of visible persistence in dyslexic children.

http://www.scholarpedia.org/article/Visual_masking - Bruno G. Breitmeyer and Haluk Ogmen (2007), Scholarpedia, 2(7):3330.

Visual masking ... briefly displayed visual stimuli that are visible when presented alone can be rendered less visible or invisible if preceded or followed by another stimulus.... Neuronal correlates of visibility and invisibility in the primate visual system Stephen L. Macknik and Margaret S. Livingstone

Flicker - A Visually Based Developmental Reading Deficit
Michael McCloskey and Brenda Rapp, Johns Hopkins University 17 March 1999; revised 6 October 1999. Available online 25 March 2002.

McGuinness D, Lewis I, 1976, "Sex differences in visual persistence: experiments on the Ganzfeld and afterimages" Perception 5(3) 295 – 301 Sex differences in visual persistence: experiments on the Ganzfeld and afterimages Diane McGuinness, Ian Lewis Received 8 December 1975 Abstract. Sex differences were investigated in two experiments on visual persistence: the Ganzfeld and the afterimage. Males were found to hold visual sensation longer than females, particularly in the Ganzfeld where there was little overlap of scores. Variability of experience in the Ganzfeld was also greater for males and they commonly reported 'blank-out' effects while females did not. There was further evidence from both experiments that females are more responsive to the long-wave region of the frequency spectrum.

Thank you for your attention.