The Educational Implications of Visual Persistence

 
 

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 email 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.

 
 
   



 
 
Implications for education
Those of you who can read comfortable at 50 ms may be a bit surprised to hear that many of us limp along at 250 ms. Those of you who struggle at 250 ms or longer will find it hard to believe that there are plenty of people who can read at 50 ms, because to us, that looks like an incomprehensible blur.
 
  The human brain did not evolve to read text. Long visual persistence presumably had evolutionary advantages in the world before text and presumably still has those advantages, but in a text orientated world, it clearly has some significant disadvantages as well. It may be, that the current design of our education system is accidentally amplifying those disadvantages.

 
  Education is a text intensive profession, which makes it rather unattractive to those of us who have longer than average visual persistence. The profession actively and passively filters out slow readers, and is therefore staffed from a biased filtrate, by people with shorter visual persistence, who happen therefore to be quicker with text, and who have no personal experience or understanding of how inaccessible the text based elements of their pedagogy are for the rest of us.

  
  The ability to read text is not directly related to intelligence. There are plenty of 'smart' people who find reading difficult, there are plenty of 'not so smart' people who can read easily, and there are many shades in between. (More research is needed here, please e-mail us if you know of any.)

 
  The people who direct education policy claim to be sensitive to this issue – but they continue to design education systems which rely heavily on text as the primary medium for conveying crucial information. The operational assumption seems to be that the ability to process text IS very closely linked with intelligence and is a good measure of the kind of intelligence they value.

  
  I am sure we have all met people who are not all that .... but are nonetheless very good readers. This suggests that the 'fast reader = smart person' is a flawed model. The reverse model unfortunately is rather self-fulfilling, because a difficulty with text is very likely to lead to poor performance, in a text based education system, and can easily lead on to a host of other related problems - in a text based education system.

  
 

So despite 30 years of 'equality' driven adjustments to our education system, (I am writing about the UK here,) this slight natural variation in our ability to process text is still being amplified and exaggerated, possibly more than before (as a result of the recent emphasis on embedded literacy), and may be producing highly discriminatory outcomes.

What a waste – an unintentional, unnecessary and easily avoidable act of discrimination – with a huge social cost.