MadSci Network: Neuroscience

Re: What are the processes of the brain and eyes when reading?

Date: Wed Jan 6 07:38:34 1999
Posted By: joshua rodefer, Post-doc/Fellow, behavioral biology, harvard medical school-nerprc
Area of science: Neuroscience
ID: 915563588.Ns

You have posed an interesting series of questions about the visual system. 
 I'll try my best to give you some of the basics and then to point you in 
some other directions where you might discover some interesting things 

To start with, the visual system is quite complex and can't be addressed 
adequately in a brief forum like this one.  However, despite its 
complexities, we (perhaps) know more about the visual system than about any 
of the other senses.  This is due, in part, to the fact that a large 
portion of the human brain is devoted to the processing of visual 
information.  Indeed, humans are predominantly visually oriented creatures 
(as are most mammals) and this no doubt played a large role in our 
evolution -- but that's getting into a whole other area.

As to your first question, the color of paper most certainly does effect 
the ability to read.  Here is a real world example that might be of 
interest to you since you may have recently acquired your driver's license 
(or may be sitting for the exam in the near future).  You probably have 
noticed that important road signs are frequently BLACK print on a YELLOW 
background.  This isn't a subtle attempt to get you to cheer for the 
Pittsburgh Steelers, but it is an effective use of science.  Our eyes 
respond best to the color yellow (it may have something to do with evolving 
on a planet surrounding a yellow star).  Thus, yellow things are easily and 
quickly noticed (like a school bus!).  Dark print on a lighter background 
produces a great deal of contrast between the print and the background, and 
thus makes it easier to detect.  Likewise, the converse (light print on a 
dark background) is also true.  Most signs that people want you to read are 
light on dark, or dark on light.  It is just easier on the eyes that way.

When you change colors to ones with less contrast, distinguishing the 
letters can be more difficult and reading could be slowed (although I could 
not find a specific study that addressed this specific question).  Think 
about trying to read something printed in red on a blue background.  Pretty 
difficult, no?!   Sometimes this lack of contrast is used for a reason.  
Chris Carter, the writer/director of TV's X-Files, often likes to keep the 
scripts for the series (and last summer's movie) a secret.  So how does he 
prevent leaks or unauthorized photocopies from being distributed?  He makes 
sure the scripts are printed in red ink on pink paper.  It's readable 
(although not as easy to read as black text on white paper), but doesn't 
have enough contrast to be photocopied.

As to the rest of your question (what does the brain do when reading...), 
that is too much information for me to summarize here (books and books and 
books!).  In brief, visual information enters your eye and travels along 
the optic nerve towards the back of your head (occipital cortex).  The 
primary visual cortex starts to process the information and from here it 
goes to other areas of your brain (such as the visual association cortex in 
the parietal lobe) for additional "processing" and interpretation.  One 
thing to keep in mind is that the different areas of the brain have evolved 
to process very specific types of visual information.  Some neurons process 
motion information, others work mainly with perceiving colors, forms or 
textures.  Up to this point in the visual system, we share most of these 
abilities with other mammals (you can test the color or movement vision of 
cats or monkeys in much the same as humans).  However, when it comes to 
reading, humans are unique.  Moreover, reading involves a great deal of 
cognitive learning and development (often studied in psychology) that is 
(obviously) only able to be studied in humans.

Distinguishing boundaries of objects (such as letters on a page, or a dog 
walking in the snow) deals with a process called lateral inhibition.  In 
plain terms, lateral inhibition is when the activity of one neuron is 
reduced by a neighboring neuron that has been excited.  This helps us 
perceive, among other things, boundaries.  It also helps create some 
interesting visual illusions.  The page below has some good ones you might 
want to check out.


Other visual phenomena, which may be of interest to you are blindsight (the 
ability of a seemingly blind persons to touch or grab objects that they 
report they can not see) or perhaps some of the various visual deficits 
(visual agnosia, simultanagnosia).  You can find out more information on 
these in textbooks or by doing a MEDLINE search.  Try using the Pub-Med 
( or Grateful Med ( 
web sites.

For a general overview of the visual system, I'd recommend looking at a 
basic biopsychology textbook.  They usually have a good overview chapter(s) 
on the subject of the visual system.  Two that have helped me through the 
years are:

Neil R. Carlson's Physiology of Behavior, (Allyn & Bacon Publishers) or
James W. Kalat's Biological Psychology (Brooks/Cole Publishers)

(I looked at both before I wrote this answer)

Also, Oliver Sacks, M.D. has written a number of good books on some of his 
more interesting neurological patients (Two of his more popular books are 
The man who mistook his wife for a hat, and, An anthropologist on Mars) 
that I would encourage you to examine.

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