NYU Researchers Discover Defining Factor for Legibility

Character size, measure, typeface … these are all generally accepted as being factors that influence legibility. Yet the study The uncrowded window of object recognition by New York University neuro-scientists Denis G. Pelli & Katharine A. Tillman published in scientific journal Nature Neuroscience advances the thesis that character spacing is the defining factor for legibility. For this at least a “critical distance” must be exceeded, to allow the brain to read the words and text without effort. When reading a book from a longer distance the letters start to amalgamate and blur. Even though this is rarely the case in daily practice, the research confirms that deciphering text becomes harder when the spacing is maladjusted. By the way the gaps between items are also crucial when viewing everyday objects – if objects are far removed their distance to each other also has to be larger.

The abstract reads:

It is now emerging that vision is usually limited by object spacing rather than size. The visual system recognizes an object by detecting and then combining its features. ‘Crowding’ occurs when objects are too close together and features from several objects are combined into a jumbled percept. Here, we review the explosion of studies on crowding – in grating discrimination, letter and face recognition, visual search, selective attention, and reading – and find a universal principle, the Bouma law. The critical spacing required to prevent crowding is equal for all objects, although the effect is weaker between dissimilar objects. Furthermore, critical spacing at the cortex is independent of object position, and critical spacing at the visual field is proportional to object distance from fixation. The region where object spacing exceeds critical spacing is the ‘uncrowded window’. Observers cannot recognize objects outside of this window and its size limits the speed of reading and search.

Personally I’m still convinced that legibility depends heavily on a combination of well-known typographic parameters, such as typeface, type size, colour, line length, line spacing, medium and also character spacing. Who needs neuro-scientists when one can rely on Bringhurst?

Header image: Willow Lineup 2 © Lars Sundström
Typeface: FF Enzo by Tobias Kvant

Tags: , , , , , ,


  1. Yeah, I would agree: it is well known that Arial is the most readable typeface…

    Posted by Klaas on Nov. 24, 2008
  2. I would like to suggest that Arial is the most read typeface by being bundled with the Windows OS, rather than the most readable one.

    Posted by Josef Go-Oco on Nov. 25, 2008
  3. Funny that considering the topic of the post that the web page doesn’t render character spacing at all well (from my view at least).

    Posted by Colin Hall on Nov. 25, 2008
  4. This of course is largely dependent on operation system, monitor, browser software etc. I think comparative studies have been conducted. :)

    Posted by Yves Peters on Nov. 25, 2008
  5. Actually, I think the the character spacing is about as good as your going to get for a web font, as Georgia is the most readable screen font available.

    Also, Arial is ripped off Grotesk junk, made as the generic Helvetica, and is only used because it ships with Windows. And if I were going to use a san serif for screen view I would throw Arial away and use Verdana, as it is the most readable screen font.

    Posted by Joseph Sims on Nov. 25, 2008
  6. Verdana is really awful at bigger sizes for headlines, though. Ugh. No matter how compelling the content, I reject sites that use Verdana in headlines. Arial isn’t great, but it’s better than Verdana.

    Posted by Steph Mineart on Nov. 25, 2008
  7. Well, Verdana is specifically designed for text use, hence it looks at its best in small point sizes, while Arial works better in larger sizes. This is why The FontFeed opted for Arial for headers.

    Posted by Yves Peters on Nov. 25, 2008
  8. @Colin Hall: Lol, that’s what I thought too. I used to use this font for my blog, but then I realised it was difficult to read and changed it to Trebuchet MS instead.

    Posted by Sonia Zuzartee on Nov. 25, 2008
  9. MS Trebuchet has the potential to be a good humanist sans for web, but IMHO the lowercase “a” looks out of balance, and the “g” is yucky. But that’s just me. ;)

    Posted by Yves Peters on Nov. 26, 2008
  10. @klaas – actually, many studies have concluded that serif typefaces are more readable than sans, so I can’t imagine a poor quality ripoff sans font ever being the most readable.

    Posted by Dan on Nov. 26, 2008
  11. My comment about Arial was meant as bit of a joke. However, spurred on by all this, I stepped into a colleague’s office who has dyslexia to ask her what the most readable font was in her opinion. Her answer was that Arial is definitely the most readable (at least as compared to Times). Has there been an actual study of readability? If so, where is it? If not, maybe it’s time to do a (reasonably scientific) study comparing the readability of various fonts corrected for spacing, leading, x-height (…), colour of paper (…..)? To put in a my own 10 cents’ worth on readability, I personally prefer slab serifs such as Chaparral.

    Posted by Klaas on Nov. 27, 2008
  12. I have not read the article. You have to pay for it.

    When discussing this, we must clearly (ha) say whether we are talking about legibility or readability? On a monitor or in print? Display or text sizes? etc.

    Verdana is infinitely better than Arial for text for both print and monitor. Arial is too condensed — it slows reading and is not as well discerned on a pixel-based monitor at text sizes. Moreover, as one ages, the condensed nature of the font becomes more problematic.

    Hence, Verdana wins by a landslide because of its more “normal” character proportions.

    I like what Josef Go-Oco and Joseph Sims said on Nov. 25.

    Posted by Robin on Nov. 27, 2008
  13. keep in mind that when you’re talking about legibility, you have to think of a lot more than what’s on the page/screen. For example a simple thing as the reader’s age greatly reduces legibility.


    Posted by Jessi Long on Dec. 1, 2008
  14. As everything in typography, it is actually a conjugation of factors. Scale has limits, just like weight, tracking and kerning. The goal is to balance the strength of every item. Typography is a team work, though the most difficult part is the spacing. You may have the perfect typeface for the job, with the perfect weight and body size, but if the spacing fails, every other choice is compromised.

    Posted by sandro lopes on Dec. 11, 2008
  15. Interesting thoughts, but I’d like to suggest expanding the conversation to typography in other-than-electronic media. Environmental and print graphic designers rely on conspicuity as much as legibility and plain old good spelling to do good work. Check out http://www.clearviewhwy.com for a fine review of some in-depth research and development on making a font go to work.

    Posted by Carl on Jan. 15, 2009
  16. My old eyes are offended by low contrast. Even a person with 20/20 tested with a high contrast test card may have trouble with low contrast of the same size. We don’t have a good handle on this..I have in mind a way to find out what people can read by assembling examples of printed material that comes to me in the mail: ads, correspondence, magazines and newspoapers. Produce a one page display of the variety of contrasts and sizes and have people read them where they normally read and mark which give them trouble. Add it all up and you get the percent of the sample population that can read each sample.
    This is not six sigma work. It is an expedient to let the population tell us “This is Ok; this is not. It might put an end to the current practice of using pale ink on pale paper. ten.nozirevnull@nedeumfg ===gm===

    Posted by G F Mueden on Jan. 21, 2009
  17. Good article.

    There is a thoughtful piece on typography as it relates to dyslexia at http://www.robsfonts.com/sylexiadproposal.html – and better than the usual ‘use arial’, something I’ve always been doubtful about.

    @G F Muerden
    Just as a quick note on contrast, WCAG2.0 gives some specific guidance on it. For example, looking just at greys on white, #969696 or darker is the recommended minimum contrast for large text (headings etc), with #777 the best practice for large text, and the recommended minimum for body text. #595959 is the best practice minimum contrast for body text.

    Posted by Liam McGee on Mar. 24, 2009
  18. Arial is great, especially when it’s in bold text. I’m sure it matters, but when someone with a learning disability has to read a paragraph with the fonts size at 10, and in italics, they’re going to have a problem. This is why computers are so great! They can zoom in on any word or object, and you can get a better look at it. This will probably be another factor in why computers are needed more and more in classrooms.

    Posted by Melinda on Feb. 21, 2011

Post a comment:


The FontFeed

The FontFeed is a daily dispatch of recommended fonts, typography techniques, and inspirational examples of digital type at work in the real world. Eat up.

  • Minicomputer
  • Segno™
  • Neutrif Studio
  • Magehand
  • Highest Praise
  • WBP Red Tape
  • YWFT Ink
  • WBP Sight
  • WBP Ripples
  • Slantinel
  • Taglocaps
  • Obstacle
  • YWFT Bitwood
  • Carrot Juice
  • Dragon Spell
  • Platz Grotesk
  • Collect Em All BB
  • New Lanzelott
  • Harajuku Script
  • Honeyguide
  • JT Marnie

Popular Fonts

  • Morl
  • Merlod
  • TT Backwards
  • Heading Pro
  • Proxima Nova
  • Nexa Rust™
  • Rosella™
  • Brandon Grotesque
  • TT Travels
  • Bourton
  • Helvetica Neue®
  • Cenzo Flare
  • Nexa
  • TT Norms
  • Aromatica
  • Gilroy™
  • Selfie
  • Avenir®
  • Moments
  • Viva Beautiful
  • Serendipity