The issue of ‘yellow’ overlays is associated, I think with the idea that ‘ it makes the text stand out’.
The fovea really only has red and green sensitive cells in it. The Blue sensitive cells are just not there. You can argue that a person will always respond to a small yellow component in a visual scene. ( exploited by wasps and poisonous ‘beasties’ warning you ‘ not to touch’! Basically any ‘yellow (red/green cell stimulating) object on a scene will elicit a saccade to it so that you can
- · work out where it is.
- · examine it.
- · avoid it.
Car rear number plates are black and yellow for that purpose ..sort of!
Lawyers I believe use yellow paper often.. Possibly for the idea of a ‘quick’ read as well.
John’s ( Stein) work on magnocellular difference ( deficit)shows a connection between blue light stimulating the magnocellular system through the blue/yellow channel and some other cells in the retina has supported the ‘idea that yellow or Blue is ‘good’ for dyslexic people and especially with his glasses from the DRT.
However in discussions with him at the Oxford Symposium, he was happy to point out that because of the pupil reflex the glasses also either decreased the red component or increased it relative to the green which made my ideas and his much closer than he had realised!
The ‘’yellow’ idea also can affect the way that the Intuitive colorimeter has been used. When I was working in collaboration with the IOO and collaborating with Cerium Visual technologies around 12 years ago, we used to send students off to a particular Hospital optometry department where they were using the Intuitive colorimeter, when following the protocols in force, it had become clear that there was a ‘definite benefit’ for the student.
Ok the rule was that ‘ the glasses colour would not be the same as the overlay that the student had chosen by the forced choice system protocols’ of the Intuitive Overlays from the IOO.
BUT at the time we were the only people actually measuring the benefit of interventions. I always try to ensure proper audit. The students came back with the coloured glasses and we compared their performance with them compared with the overlays and the coloured computer screen.
This particular leading hospital suddenly started to send everyone back with yellow glasses. The students got very little benefit from them.
I followed up with conversation with the quality control people at Cerium, where the glasses were being made.
No one there had noticed any change, there was no auditing system in place. When I checked with the hospital, it turned out that the person trained to use the Intuitive Colorimeter had moved on and a new person was now in charge of it. They had never been on the course with Cerium and thought that ‘Yellow was good for dyslexics’ and had effectively been guiding the students!
There is a tendency to use ‘cream’ or buff as well but this is likely to be just about reducing the luminance down to around 80% which is you look at the data we have collected appears to be the modal luminance for the thousands of dyslexic students my colleagues have worked with.
There is no data supports the ‘colour’ cream as being better than any other ’pastel shade’ it has just become a bit of an accepted myth propagated by many websites that give it as a default,
One of the problems of these myths is that because most people/students do not respond positively to them there are loads of false negatives and as a result nobody actually looks for what might work in a logical fashion. This leaves many ‘coping’ with avoidable visual problems, small visual attention spans and reinforces the idea ‘ that you have to live with your problems’