Saturday, November 05, 2011

Visual Overload and Visual Crowding - When More Means Less

"If there were only 10 problems on a page, I could do them all. But when there are 40 on a page, I can't do any of them." - 10 year old student

Visual overload and visual crowding are common problems in every school classroom or company work group, but the mistakes and errors that result from them are rarely recognized or traced back to their true source. It is a paradox - the more you see, the less you see, but it all makes sense if one recognizes that a child or an adult's visual working memory deskspace can become easily overloaded.

For visual scientists, visual crowding is a specific term that refers to a greater difficulty in seeing when other visual objects are present. When we look at a complex scene, for instance the picture above, it is impossible to take in all the other visual details. It's what causes some people to overload when they go to large gatherings like music concerts, Disneyland in the summertime, or a crowded Home Depot, but also children in crowded classroom, all-school assembly, writing on a scantron, or completing Mad Math Minutes.

Signs of Visual Overload
- Longer processing time, slow reading, and incomplete work on crowded worksheets
- Tantrums, irritability, and overload behaviors in crowded environments
- 'Careless' mistakes and unintentionally skipped problems on worksheets and tests
- Missed words or endings while reading, need to re-read words

Interestingly, a recent report on Visual crowding, reading, and dyslexia found that a visual crowding effect significantly contributed to slowness in word reading, and dyslexics as a group found that increased spacing between letters improved readability. The critical spacing threshold for readability was significantly higher for dyslexics as a group compared to non-dyslexic controls, so it became easier to identify a letter away from the center if the spacing between characters were greater.

Take-home points:

- Critical print size is larger for dyslexics than controls
- Critical spacing between characters is larger for dyslexics than controls
- Reading rate improves with print size to a critical point
- Explains why many dyslexics with excellent verbal funds of knowledge still have trouble reading long words

Classroom and Test Accommodations

In the classroom, more attention should be paid to print size and spacing in daily classroom (worksheets, handouts) and testing materials (as many as 1 in 5 students are dyslexic), and print size and spacing should be considered when purchasing books for students.

Large print books and reader glasses may help some students, whereas font differences (serifs like Times New Roman or hand-written fonts like Papyrus or Comic Sans often preferred) may be more important for others. For students with narrow visual spans (see only few letters at a time), serifs or handwritten fonts may dramatically lessen the work of reading - with serifs or personalized font shapes - it is easier to perceive the overall shape of words, so that even if a reader only sees the first and last letters and general shape of the word, they can make an educated guess about what that word might be even though they are unable to see all the letters.

Many of you are probably aware of this meme from the Internet:


Matt Davis has written more about the science and history of the discovery of this effect here.

Eide Neurolearning Blog: Blessing and burdens of vivid visual thinkers
Eide Neurolearning Blog: Video game training increases visual span
Photo: scantron


  1. Thank you for the enjoyable and informative post on visual crowding. This is an area that developmental optometrists deal with in a variety of ways.

    Individuals with visual forms of dyslexia, and those with amblyopia both exhibit visual crowding, and this isn't coincidental, as both are considered to be developmental anomalies of spatial vision. Young children with normal visual abilities exhibit visual crowding when reading letters on an eye chart that reduces as they mature.

    The suggestions that you give for reducing visual crowding are excellent. But there are also active therapy procedures that can be done to reduce the effects of crowding. As an example, see:

    Thank you again for your wonderful blog.

    Leonard J. Press, O.D., FCOVD, FAAO
    The Vision & Learning Center
    Fair Lawn, New Jersey

  2. I just discovered your blog and look forward to diving in and exploring the richness. As a mother of a gifted visual/spatial child who is in a very traditional school, your wealth of information will be an asset. Thank you.

  3. Very interesting article, thank you.

    The opposite effect is equally interesting, I think, when immense complexity in a visual scene is perceived as a simple pattern because of the way it is organized. This happens sometimes when you take a very dense visual scene and view it from 40,000 feet.

    In the old days of computer printing, before there was control of individual pixels, we used to have printers that used special characters as pixels based on their optical density. You could print something that appeared visually as a lifelike portrait of a person. Then when you got very close to it, the visual complexity would be overwhelming because you would see the individual characters rather than the overall pattern.

    Importantly, what exactly makes a visual scene complex depends a lot on the specifics of how visual cognition works, rather than on our preconceptions about what it means for something to be complex from another perspective.

    Vision seems to have its own fascinating rules.

  4. Anonymous6:55 PM

    I have learned (as an adult) that if I place either a yellow or rose translucent cover over a white w/ black page of writing, the letters 'become less crowded'. I've associated it with other sensory processing issues I have along with an inability of the cerebellum to gate the information that is coming in.
    thank you for the post.

  5. Anonymous11:08 AM

    Highly ironic article about visual overload. I can barely read it because of all the pictures.

  6. Thanks, Anon. Point well taken.

    I've removed the top picture.

    The ones who have to 'learn' about visual crowding are the ones that don't experience it.

    I left in the scantron, but cause that's the example that really needs accommodating for tests and too many professionals just don't think about it.

    : )

    1. Interesting points - Just one thing I'd like to note about the scantron comment. Not too many professionals (which I am assuming you are talking about teachers) rethink scantron or testing materials because they are using whatever was purchased / created by a printing/publishing/ or technology company and every decision about the page design, font, scantron form has to do with cost of ink, paper, or hardware and not about accommodations for the enduser. In fact, I would venture to say educators are often "stuck" with what they "get".

      In my school district, we have purchased from a company that can provide large-print texts and braille items for classroom use for those students with severe vision problems. But again, you are correct - the teacher has to be aware ahead of time who has what vision problems and what tests - like state assessments - will look like, in order to realize a student will need the large-print version.

      We have new state assessments coming this year with a lot more passage reading - the samples have not been very high quality and so again we can't make an informed decision in advance of the test regarding vision issues except for only the most obvious student vision needs.

      Also something to consider - Common Core assessments - which are assessments that will be "common" between all 50 states - are supposed to be moving from paper to computer screen for 2013-14. Tell me more about the impact on students for an hour-long test (for average learners) and extended time for students with disabilities who are allowed up-to-double the time for completing the test. Currently the paper NYS-mandated tests are an hour-long sitting without breaks unless a child has a disability (and then the child may be given even more time). I'd LOVE to hear your response to this.

      Thanks - and this is a cool blog. Just found this today.