- From: Laura Carlson <laura.lee.carlson@gmail.com>
- Date: Wed, 14 Jun 2017 08:53:38 -0500
- To: Wayne Dick <wayneedick@gmail.com>
- Cc: public-low-vision-a11y-tf <public-low-vision-a11y-tf@w3.org>
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 Wednesday, 14 June 2017 13:54:11 UTC