Is Crowding a Form of Visual Sensory Overload?

Crowding - WaldoThanks to one of our faithful readers, Dr. Michael Margareten, who always points out interesting articles to me, most recently this gem just published in the Journal of Vision.  “Where’s Waldo” is a familiar example of visual crowding, and as the article defines it, crowding represents a breakdown of object recognition thought to be due to combining extraneous features from neighboring objects with those of the target.

Consider further this example used by the authors:

Crowding - Objects

When you fixate the small square to the left of the objects on each row in Column A, it is very difficult to identify the center object.  In contrast if you fixate the square in Column B, the center object in each row is much easier to identify.  Yet, if you got out your millimeter rule and measure the space between the center object and the surrounding letters, you’d find their identical!  The authors even imply that some children may reverse or flip the orientation subconsciously if this reduces the crowding effect.

We’ve blogged quite a bit about the concept of visual crowding and its relationship to amblyopia and to reading in particular.  This article adds another dimension to our understanding of the concept. It’s not just the inter-letter spacing that has such a profound effect.  It’s also the complexity of the visual field in terms of the configuration of letter groupings within given words, and from one word to the next.

This adds to our understanding of why so many children who are hooked on phonics are excellent at identifying words correctly when presented with vertical word vocabulary lists …

Word List

… but stumble on reading fluency when required to track laterally across the page.


It is my contention that these children, or patients with reading difficulties recovering brain injury affecting the visual reading network, or individuals with amblyopia, are highly susceptible to a form of visual sensory overload that occurs in crowding of this nature.  Invariably, any lens or prism or set of therapy procedures that can stabilize or minimize crowding effects can be highly beneficial in transferring to increased fluency while reading.

Which vision therapy procedures can you think of to lessen susceptibility to crowding?

3 thoughts on “Is Crowding a Form of Visual Sensory Overload?

  1. Interesting blog, Dr. Press! Crowding is an important phenomenon to address since many patients and parents don’t understand why this occurs. In therapy, modification is key. For example, instead of a crowded 10×10 letter Hart Chart we can use a 5×5 chart to increase the spacing between the letters and decrease the complexity of the field.

  2. It is true overcrowding affects the reading profoundly for students with reading difficulties . Another suggestion beside enlarging ( depends on the individual size preference) is the background colour of the paper and the print .

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