Re: Letter and Word Spacing: Final Analysis

Apologies, I realised I missed this thread last month.

With that level of spacing being added, I think we have to stop applying it to all text on the page.

It looks like it would result in well over 10% increase in text-width, in the region of 30%?

As soon as people test that in practice, it will blow away many navigation mechanisms, and areas of layout that are constrained.

I suggest that we apply it to ‘blocks of text’:
https://www.w3.org/TR/WCAG20/#blockstextdef 
“more than one sentence of text”.

E.g. “…by adapting all of the following for blocks of text:”

Does that raise alarm bells for anyone?

-Alastair



On 16/06/2017, 18:54, "Repsher, Stephen J" <stephen.j.repsher@boeing.com> wrote:

    All,
    
    I reviewed the McLeish study as well and I think I concur mostly with Wayne.  It's worth noting though there is large scatter in the data though, especially above 0.15em ("normal + 30%" in the article).  The trend line shown is not described, but appears to be a simple least-squares fit.  Given the scatter, the choice of curve fit would also affect interpretation.  Based on this study, I think we need to cap any SC number to less than 0.15em, so I'm fine with the original 0.12em.
    
    I also would subscribe to Wayne's theory about RSVP being a very unrealistic approach to measuring reading speed for folks with low vision.  There's no way it's a Galilean invariant process.
    
    One thing I'd disagree with though is about word spacing.  We either need to find a study on this or apply a proportionality rule or some other logic.  As letter spacing goes up, the ratio of space between words to space between letters goes way down, so eventually it'll just look like a string of letters.  Do we have any articles that studied them together?  If not, I'd set word spacing so that ratio remains roughly the same.
    
    I do need to go back and fix my equations though because I had assumed letter spacing was not added between words.
    
    Steve
    
    -----Original Message-----
    From: Laura Carlson [mailto:laura.lee.carlson@gmail.com] 
    Sent: Wednesday, June 14, 2017 9:54 AM
    To: Wayne Dick <wayneedick@gmail.com>
    Cc: public-low-vision-a11y-tf <public-low-vision-a11y-tf@w3.org>
    Subject: Re: Letter and Word Spacing: Final Analysis
    
    Hi Wayne,
    
    In case you missed this study when Mike Gower posted it on GitHub:
    
    Extra-large letter spacing improves reading in dyslexia http://www.pnas.org/content/109/28/11455.full

    
    A while back I found Legge's Aug 2016 study, "Reading Digital with Low Vision". He says: "Overall, the evidence indicates that increasing spacing between letters is not helpful..."
    http://search.proquest.com/docview/1825176282

    
    Kindest Regards,
    Laura
    
    On 6/14/17, Laura Carlson <laura.lee.carlson@gmail.com> wrote:
    > Hi Wayne,
    >
    > Thank you!
    >
    > I updated the folks on GitHub:
    > https://github.com/w3c/wcag21/issues/78#issuecomment-308421776

    >
    > And asked Jim to put this on a future LVTF agenda.
    >
    > Kindest Regards,
    > Laura
    >
    > On 6/13/17, Wayne Dick <wayneedick@gmail.com> wrote:
    >>  *Letter and Word Spacing* *Summary of Results:*
    >>
    >> For best reading results the spacing should be .25em maximum. 
    >> However, the loss of performance between .12em and .25em is less than 
    >> 1/4 in reading speed. I think .15em is the best because that gives 
    >> 95% of the benefit.
    >> After that there is almost no benefit. After .25em there is none.
    >>
    >> Word spacing may not be necessary, because browsers tack on the 
    >> letter spacing to the normal word spacing anyway.
    >> *Good News / Bad News*
    >>
    >> The good news. Alastair and I are both right in our calculations.
    >>
    >> The bad news. Alastair and I are both right in our calculations.
    >>
    >> We have a serious political decision to make.
    >> *Analysis*
    >>
    >> My letter spacing was based on an article, “A study of the effect of 
    >> letter spacing on the reading speed of young readers with low 
    >> vision”, Eve McLeish, Visual Impairment Service, UK (British Journal 
    >> of Visual Impairment 25(2) 2007). In this article, the author builds 
    >> a table for spacing of typed assignments for children with low 
    >> vision. The formula she used was STEP=[fontSize/20], for each test 
    >> bracket. Each STEP represents increasing the letter spacing by 1/10 
    >> of the letter size. She used points for her font size but we will use 
    >> pixels.  McLeish found significant results with reading speed up to 
    >> n*STEP for n=1… 5. However, the slope went from steep to horizontal 
    >> in this range. It was concave down going flat at n=5. When I computed 
    >> these results, I started at n=5. Example: for font size of 16px, 
    >> 5*STEP = 5(16px/20)=4px=0.25em. The formula works the same for all 
    >> font sizes.
    >>
    >>
    >>
    >> I got to these values the first time and noticed that the performance 
    >> curve really flattened between n=3 and 5. It grew from 0 to 20% 
    >> increase in reading speed from n=0… 3. Then grew from 20% to 22% 
    >> between 3 and 5. I should have selected 3 first and got 3*.8=2.4px= 
    >> .15em.  Fear of developer response, got the best of me, so I 
    >> suggested the .12em. At that size, the performance curve still gave a 
    >> 15% increase in reading speed.
    >>
    >> For testing, I used Firefox with, Tahoma and the text, “Lorem ipsum 
    >> dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor 
    >> incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, 
    >> quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea 
    >> commodo consequat.
    >> Duis
    >> aute irure dolor in reprehenderit in voluptate velit esse cillum 
    >> dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat 
    >> non proident, sunt in culpa qui officia deserunt mollit anim id est 
    >> laborum.” I got the following results:
    >>
    >> Let Average Char be the number of pixels taken by an average 
    >> character in the passage.
    >>
    >> Letter Spacing
    >>
    >> Average Char
    >>
    >> Increase
    >>
    >> Normal
    >>
    >> 7.004px
    >>
    >> 0
    >>
    >> 0.12em
    >>
    >> 8.921px
    >>
    >> 1.917px or 27%
    >>
    >> 0.15em
    >>
    >> 9.404px
    >>
    >> 2.4px or 34%
    >>
    >> 0.25em
    >>
    >> 11.004px
    >>
    >> 4.0px or 57%
    >> *Controversy*
    >>
    >> Aside from the huge impact on layout there are other difficulties.
    >>
    >> The research is mixed. The benefits of letter spacing are measured by 
    >> various experiments in the range from no effect to simply miraculous.
    >> McLeish is in the middle; her methodology is sound, and she observes 
    >> the impact in the most natural setting. Her findings rang true with 
    >> my experience.
    >>
    >> The most significant article that shows no effect is: The effect of 
    >> letter spacing on reading speed in central and peripheral vision by 
    >> S. T. Chung (Investigative Ophthalmology and Visual Science, 2002 
    >> Apr, 43(4):1270-6).
    >> Chung’s methodology is sound, but she uses a different instrument for 
    >> measurement. McLeish uses flash cards while, Chung uses Rapid Serial 
    >> Visual Presentation (RSVP). The words are drifted past at varying 
    >> speeds.
    >> Chung’s
    >> theory is that an individual can read faster when more letters are 
    >> fit in the most sensitive reading zone of a reader’s retina. 
    >> Increased letter spacing reduces this value and therefore reading speed must suffer.
    >>
    >> Both authors are correct, in my opinion.  This needs to be tested of 
    >> course, but here is my reasoning. McLeish’s use of cards, forces the 
    >> participant to orient their most sensitive reading zone each time the 
    >> card is presented. Thus, McLeish measures orientation and 
    >> recognition. Chung uses text that drifts into the participants 
    >> optimal reading zone, so no orientation is needed. This would mean 
    >> that the benefit in letter spacing would be in helping the reader 
    >> orient their most sensitive reading zone to the target.  That is just 
    >> a theory, but it does explain the difference in two well designed 
    >> studies.
    >>
    >
    >
    > --
    > Laura L. Carlson
    >
    
    
    --
    Laura L. Carlson

Received on Tuesday, 11 July 2017 16:12:25 UTC