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The Science of Word Recognition 430

neile writes "I stumbled across a fascinating paper over at the Microsoft Typography site today that provides a really nice overview of the different theories on how humans read. If you thought we read by recognizing word shapes, think again! With the assistance of fancy eye-tracking cameras researchers have been able to devise several clever experiments to give us new insight into how reading works." We've linked to some of Larson's work previously.
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The Science of Word Recognition

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  • by Anonymous Coward on Thursday September 02, 2004 @05:15AM (#10136730)
    His "word shape" matrix with "than" "tban" "tnan", etc; could be more easily explained by saying that people pay more attention to tall letters than short ones. That would explain why 'tban' gets caught more than 'tnan' just as well as word-shape arguments.

    To make it more obvious, stick a tall letter in a word that only has short letters and you'll come away thinking word shape does matter.

    (or did he explain it... there were way to many words and way too few glossy pictures in that article for me to comprehend it)

  • Eye movements? (Score:5, Interesting)

    by ImaLamer ( 260199 ) <john,lamar&gmail,com> on Thursday September 02, 2004 @05:19AM (#10136743) Homepage Journal
    With the assistance of fancy eye-tracking cameras researchers have been able to devise several clever experiments to give us new insight into how reading works."

    Oh they must have been using EyeQ [infmind.com]....

    I can read at 44692 words per minute! Thanks for posting that long article for me to read, I needed the exercise.

    And thank you EyeQ! Your the greatest!

    Really though, they say that the more letters/words mean faster reading times [microsoft.com]. It's true. Think about a book or article you've read. When the words are together on the page it's easier to read because your eyes can jump around letting your brain fill in the blanks.

    Ever read something that made sense but you couldn't quote it word for word? It's likely because you read in this same way.

  • by DrFrasierCrane ( 609981 ) on Thursday September 02, 2004 @05:22AM (#10136756) Homepage
    While reading the article, I suddenly become hyper-aware about how I was reading the article. :-)

    Don't let the Microsoft name scare you off - the article makes for a fascinating look (pun intended) into how we read. I wonder, though, if these findings are duplicated with written Oriental languages.
  • by mocm ( 141920 ) on Thursday September 02, 2004 @05:22AM (#10136757)
    Since most people in the world don't use the latin alphabet, it would be interesting to find out how word recognition works for them. And how they read words in our alphabet.
  • Re:I love how (Score:3, Interesting)

    by defMan ( 175410 ) on Thursday September 02, 2004 @05:34AM (#10136789)
    I would personally be very interested in seeing english compared to dutch or german. In those languages (i'm a native dutch speaker) the word order is much more flexible and the determining verb often comes very late in the sentence. In german this is more prominent than in dutch.

    I just searched around on google and these documents come up
    Word Order in German [about.com]
    Kathol's analysis of German Word Order [let.rug.nl]

  • How we read... (Score:2, Interesting)

    by stupid_is ( 716292 ) on Thursday September 02, 2004 @05:34AM (#10136791) Homepage
    A while ago I was emailed something that stuck out from the usual chain/joke/... flood. Basically it had a very long and badly spelled sentence, where the only rules followed were that the first and last letter in the word were in the correct position. You could read it easily. Go figure!

    Hree is an epamxle of jsut taht, it's qitue esay to raed, ins't it? Agulohth it can get plluartraicy hrad wtih the lgnoer wdros.

  • rn vs. m (Score:1, Interesting)

    by Anonymous Coward on Thursday September 02, 2004 @05:41AM (#10136811)
    My native language is not English. Since the very early days of English learning, I've noticed there are certain vague character combinations: (1) rn vs. m; (2) l vs. 1.
  • by PotatoHead ( 12771 ) * <doug&opengeek,org> on Thursday September 02, 2004 @05:42AM (#10136814) Homepage Journal
    I found myself becoming aware of how I read while I read. Fun! I agree with the author regarding letter recognition. The parallel aspect of word recognition is very interesting as well because it begins to explain why we are albe ot raed srcambled txet os eaisly!

    Also, more work needs to be done to consider the visual cues outside the focus of attention. It is here that, I believe, shape and form cue the reader, more than letter shapes do, as to the potential content of the text to come. (Exactly how is for the geniuses.)

  • Re:I love how (Score:5, Interesting)

    by ImaLamer ( 260199 ) <john,lamar&gmail,com> on Thursday September 02, 2004 @05:44AM (#10136817) Homepage Journal
    You're right. It would seem that for better analysis comparing Hebrew/Chinese to English would be better.

    Maybe we can learn even more about our way of reading, like: Is it the most efficient?

    Is right to left, or left to right the best way to go.

    Interesting side note (don't know why I'm bringing this up...) President #20, James A. Garfield could write in both Latin and Greek at the same time?

  • Re:Reduced Redudancy (Score:5, Interesting)

    by Placido ( 209939 ) on Thursday September 02, 2004 @06:07AM (#10136897)
    >> How else would be understand a sentence like "The boy ate a ham___er" (with a few letters obscured)?

    What a way to prove your point. I kept thinking "hamster", "hammer" and then eventually realised that I didn't spot your miss-spelling of 'we' and that I read right over it and filled in the blank.
  • or maybe it's both? (Score:5, Interesting)

    by Illserve ( 56215 ) on Thursday September 02, 2004 @06:14AM (#10136919)
    If there's one real take-home lesson of brain-design from cognitive science, it's that the brain tends to do everything several different ways in parallel, and then use the results from all of them.

    Obviously it can't all be shape, there are plenty of words with identical shapes and yet these are distinguishable.

    But it could certainly be true that we use shape and parallel letter recognition at the same time. Shape narrows the field of possibilities from millions to a small handful, and then parallel recognition chooses one of the options.

    Whatever happens, you can be sure it's terribly complicated, extremely robust and very efficient.

  • Re:Reduced Redudancy (Score:2, Interesting)

    by Da Twink Daddy ( 807110 ) <bss03@volumehost.net> on Thursday September 02, 2004 @06:16AM (#10136928) Homepage
    I filled in the blank with hamster [Making it: "The boy ate a hamster"], but maybe I'm just an oddity.
  • Don't shout! (Score:5, Interesting)

    by meckardt ( 113120 ) on Thursday September 02, 2004 @06:34AM (#10136977) Homepage
    From the article: ...lowercase text is read faster than uppercase text. This could also explain why nobody likes to read email where the other person uses all caps.
  • FTA... (Score:3, Interesting)

    by Anonymous Writer ( 746272 ) on Thursday September 02, 2004 @06:45AM (#10137008)
    Why I wrote this paper

    I am a psychologist who has been working for Microsoft in different capacities since 1996. In 2000 I completed my PhD in cognitive psychology from the University of Texas at Austin studying word recognition and reading acquisition. I joined the ClearType team in 2002 to help get a better scientific understanding of the benefits of ClearType and other reading technologies with the goal of achieving a great on-screen reading experience.

    I'm surprised this guy is actually working with ClearType. That is just a simple way of making characters appear better by using sub-pixels to increase character resolution. I would think this type of work would be better applied in optical character recognition, maybe even with cursive handwriting.

  • by BigRedFish ( 676427 ) on Thursday September 02, 2004 @06:51AM (#10137018)

    The FArticle does, in fact, address this, though not directly - it puts forth a theory that all letters in a word are absorbed simultaneously, and the brain re-orders them. This is given as theory #3, admittedly a ways down.

    This gets me thinking, though, about the importance of context. If you drew the letters PLEORBM in a Scrabble game, it might take a while to see the word staring at you. But in the context of a (mangled) sentence: "you can sitll raed tish wouthit a pleorbm," it much more easily jumps out. Interesting.

  • by achurch ( 201270 ) on Thursday September 02, 2004 @06:55AM (#10137026) Homepage

    Infants of English-speaking parents easily grasp the Korean distinction between a cylinder fitting loosely or tightly into a container. In other words, children come into the world with the ability to describe what's on their young minds in English, Korean, or any other language. But differences in niceties of thought not reflected in a language go unspoken when they get older.

    Absolutely. And adults can "relearn" those distinctions, too; I found that as my Japanese studies progressed (started at 19, pretty close to native now) the range of things I was able to think about expanded considerably--so much so that now I sometimes have trouble speaking to people in English because English doesn't have a word for the concept I'm thinking about.

  • Re:How we read... (Score:3, Interesting)

    by mikael ( 484 ) on Thursday September 02, 2004 @07:06AM (#10137061)
    Interesting. Maybe word recognition uses a small cache to perform error correction if characters are swapped around by 2-3 spaces. In the case of the reversed characters, this won't work.

  • Re:Quotation (Score:3, Interesting)

    by Richard_at_work ( 517087 ) <richardpriceNO@SPAMgmail.com> on Thursday September 02, 2004 @07:10AM (#10137068)
    There was a slashdot story a while back which basically stated exactly that quote. Basically you could easily read an entire book where the words were made up of the correct starting character, the correct ending character, but the middle of the word it didnt matter what order the characters came in.

    For example: "sadhoslt nwes for nrdes. Sfutf taht mrttaes". (I think ive got that correct, someone will obviously correct me if not :))

    Your brain didnt need the middle of the word to understand the word when placed in a sentance. So long as the word was the correct length, your brain could extrapolate the meaning and create a meaningful sentance out of it.
  • by SammyTheSnake ( 630196 ) on Thursday September 02, 2004 @07:22AM (#10137103)
    I once saw a little article in a free-on-the-train paper demonstrating that we mostly read the top half of a line of text. Try it some time, cover up the bottom half of a line of text and read it, then cover up the top half of the next line of text and read that. Which is easier?

    Cheers & God bless
    Sam "SammyTheSnake" Penny
  • by ajs318 ( 655362 ) <`sd_resp2' `at' `earthshod.co.uk'> on Thursday September 02, 2004 @07:23AM (#10137106)
    They probably have already written papers on it ..... in their own languages.

    Want my theory? I think the brain uses multiple techniques in parallel, then releases resources from the ones found to be going nowhere. So at any one time you may be trying to read a word letter-by-letter, recognising the word from the Bouma shape, and picking likely words from context. The different techniques will have different successes depending on various factors (clean type vs. messy handwriting, familiar vs unfamiliar words, &c). So my theory is that the brain is trying various methods at the same time, each narrowing down the possibilities, and just goes with whatever produces a result first. As soon as that happens, any half-finished tests in progress are scrapped and their resources deallocated. The eye movements may well have something to do with this ..... different reading techniques require different resolutions, the eye is great at recognising outlines but needs to zero-in on details, once a clue is established from the word envelope. There is evidence that fonts such as Times are more readable than Helvetica, so maybe serifs add recognisability in their own way? And if this is what is happening, then it would explain some of the test results in the article too, since they were looking for a single technique in use at any one time.

    If all this sounds inefficient, you have to remember that human beings are optimised for non-optimum conditions ..... for instance, we have kidneys that pack up if you drink nothing but de-mineralised water, and an immune system that goes berserk and tries to poison you with histamine if it doesn't get enough germs to fight off.
  • Re:I love how (Score:5, Interesting)

    by dave420 ( 699308 ) on Thursday September 02, 2004 @07:27AM (#10137121)
    No, there's lots of study on the matter, and it's shown that Chinese people interpret their written language in a completely different part of the brain than english-reading people. That fact alone means a completely different method is at work... :)
  • by ideonode ( 163753 ) on Thursday September 02, 2004 @07:52AM (#10137211)
    I cdnuolt blveiee taht I cluod aulaclty uesdnatnrd waht I was rdanieg - the phaonmneal pweor of the hmuan mnid. Aoccdrnig to a rscheearch at Cmabrigde Uinervtisy, it deosn't mttaer inwaht oredr the ltteers in a wrod are, the olny iprmoatnt tihng is taht the frist and lsat ltteer be in the rghit pclae. The rset can be a taotl mses and you can sitll raed it wouthit a porbelm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe.
  • Re:Quotation (Score:3, Interesting)

    by Lars Clausen ( 1208 ) on Thursday September 02, 2004 @08:14AM (#10137317)
    It also turned out to be mostly urban legend. There was some related research, but none that stated that claim. Bdeeiss, if taht was true, we cloud imoprve ceioomprssn aghilmorts by sinortg the mddile leertts aaabcehilllpty, scine tehir piinoosts are iaaeimmrtl.

  • Re:Ahem... (Score:1, Interesting)

    by Anonymous Coward on Thursday September 02, 2004 @08:35AM (#10137418)
    Man, that site is crazy. People complaining about someone wearing the US flag as a skirt, and claiming the Constitution is "one of the top 5 achievements in human history" (so which of the wheel, control of fire, agriculture, writing, and Slashdot is it supposed to be better than?)

    To my non-American eyes, that is exactly the sort of thing that makes America look ridiculous. Sorry, but it is. Those people would only look marginally crazier if they were bowing down before a statue of a giant slug and hailing it lord of mankind.
  • by Lars Clausen ( 1208 ) on Thursday September 02, 2004 @08:37AM (#10137426)
    As a non-native (but fluent) speaker of English, and the husband of a fluent English speaker learning Danish, I can tell you quite well that there are many concepts that have a single word describing them in Danish but not in English, and vice-versa. Some words are normally considered equivalent but have slightly different extents ("pink" covers more colors than the common translation "lyserød", for instance).

    The grandparent also didn't say "couldn't be expressed", but "has no word". Given enough verbiage, you can (probably) express any word in one language in any other language, but that's not what you want to do in conversation.

    And if the "language of Shakespeare" is so all-encompassing, why has English since then been stealing words from other languages like a slum rat during a riot in a shopping mall? Mind you, I think this is a good feature that adds expressiveness to the language, but it clearly shows that there are things that English speakers consider important enough to be able to express succinctly that they'll bring in foreign words for it.

  • Re:I love how (Score:4, Interesting)

    by julesh ( 229690 ) on Thursday September 02, 2004 @08:39AM (#10137442)
    Is right to left, or left to right the best way to go.

    I remember reading about an interesting study into this. Apparently, there are a small number of people who have a particular form of brain damage which effectively reverses their perception. These people, if they were originally educated to read/write left to right, would afterwards naturally read/write right to left, or vice versa.

    Apparently, once they get used to using their right hand with a style similar to that a left-hander would use (or vice-versa) they can read & write in the opposite direction at roughly the same rate a normal person can in the usual direction. The conclusion: the difference is not noticeable; neither left to right nor right to left is substantially more efficient (or any difference is also negated by the brain damage these people have suffered).

    No, I can't cite references. I just came across it about 10 years ago, I don't even remember what I was studying at the time.
  • amusing test... (Score:5, Interesting)

    by zozzi ( 576178 ) on Thursday September 02, 2004 @08:43AM (#10137463)
    I enjoy giving people this test: Write a long sentence and make sure that the last word of the sentence is a filler word. Then write that filler word again at the start of the next sentence and write some more. Eg:
    Yesterday I went to the beach and saw the
    the boat I always dreamt about.
    ~ 7 out of 10 people fail to spot it, even if told beforehand there's an obvious error. Somehow music people are more prone to spot the error straight away.
  • Re:I love how (Score:3, Interesting)

    by antifoidulus ( 807088 ) on Thursday September 02, 2004 @08:59AM (#10137568) Homepage Journal
    I wish they would have expounded on what they meant. Because the "sound" of a word in Chinese is pretty much the same as it's meaning. Yes, the characters do have meanings, but in Chinese(for the most part, there are some exceptions) each character only has 1 sound. The sound is exactly how you would pronounce the word if you were speaking, so I'm not sure what they mean by saying that children process the sound and the meaning seperately. Or maybe it's the difference between how a person understands a language when it is being taught as a 2nd language vs. a native one.
    It gets a bit different for Japanese though. In Chinese(once again, for the most part) you can process character by character and read the sentence. However, because Japan had to force the Chinese character system to it's language(and also borrowed readings, then newer readings without changing the old ones) each character has usually 2 readings, some only 1, some much more. How you read the character depends on the characters around it. To a certain extent it's like English, you really cannot read it character for character phonetically, you have to process blocks. I wonder if the Japanese reader uses the same parts of the brain as the English reader, or Chinese reader, or both.
  • Source code? (Score:3, Interesting)

    by maxwell demon ( 590494 ) on Thursday September 02, 2004 @09:00AM (#10137581) Journal
    While the study is certainly about reading English texts, could one draw some conclusions about the readability of source code? I guess at least the finding that whitespace governs the jumps of our eyes might have some relevance here.
  • by peter303 ( 12292 ) on Thursday September 02, 2004 @09:11AM (#10137719)
    I am somewhat fluent in Chinese. Though syllables in Chinese (and Korean) approximately fit into squares, they share two characteristics with alphabetic word shapes:

    First, Chinese characters are often composed of several smaller characters, 500 or so, instead of the 70'ish letters and numerals (including capitals) in English. We say such a character may have a "moon" sub-character on the left, a "white" on the right and so on. The sub-characters can be partial clues to meaning and pronunciation (e.g. a left moon usually signifies part of a body, and the a right moon means its sounds like "bai"), but there are no steadfast rules. Just like in English where the pronunciation can vary from the spelling, and the whole meaning vary from those of the prefix and root. But Chinese breaks the rules more often, probably since many of the characters have been around 3000 years- seven times longer than modern English spelling rules. The Korean writing system is totally planned and recent, so it is very logical. The sub-characters represent the beginning, vowel, and end of a syllable, gracefully packed into a square.

    Second, you can trace the boundaries of Chinese characters too and see distinguishing characteristics. They might have a gap in one corner, a ragged stroke defining an edge, etc. Just like in English words a learner will move from observing the strokes and sub-characters into the gestalt of the whole character. Just like any other language, chinese characters are contextual. Combinations are sematically constrained to one to four syllable word. And they are grammatically constrained to expect nouns, verbs, modifiers, etc, in certain sequences.
  • by lazyl ( 619939 ) on Thursday September 02, 2004 @09:13AM (#10137741)
    It makes a big difference if your messed up words use common letter patterns (what, in the article he called 'Psuedowords'), or not.


    'uesdnatnrd' wasn't to hard to recognize beacuase 'uesd' and 'tnrd' aren't letter patterns that exist in real words. So the mind works quicker to rearrange the letters to find a real word.

    'aulaclty' was much harder because it's almost pronouncable. 'lac' and 'lty' are common patterns from real words, and 'aul' might not be common but it's pronouncable.

    Just an observation.
  • by toby ( 759 ) on Thursday September 02, 2004 @09:47AM (#10138097) Homepage Journal
    Larson presented this paper at the 2nd international Conference on Typography and Visual Communication [www.uom.gr] in Thessaloniki, July this year. Other speakers, in particular Peter Enneson [www.uom.gr], questioned some of his methods and conclusions, and the paper - as convincing as it appears at first glance - should definitely be taken with a grain of salt.

    Following a day's sessions on legibility and word recognition, the Thessaloniki conference held a round table on legibility and the processes of word recognition, chaired by John Hudson and participants Mary Dyson, Hrant Papazian, Kevin Larson and Peter Enneson.

  • Re:REKANYZE! (Score:5, Interesting)

    by iamacat ( 583406 ) on Thursday September 02, 2004 @10:41AM (#10138652)
    Don't give any ideas to spammers on how to sneak their "pneis elnraegemnt ceram" past the filters. I do suspect that the effect is local to the small group of letters and long words that are totally randomized will be difficult to read.
  • by MegaFur ( 79453 ) <wyrd0 AT komy DOT zzn DOT com> on Thursday September 02, 2004 @11:03AM (#10138966) Journal

    The grandparent also didn't say "couldn't be expressed", but "has no word". Given enough verbiage, you can (probably) express any word in one language in any other language, but that's not what you want to do in conversation.

    The approprately clunky sounding phrase to express the thought related in your second sentence is "concatenative assemblage".

  • Re:Reduced Redudancy (Score:3, Interesting)

    by nine-times ( 778537 ) <nine.times@gmail.com> on Thursday September 02, 2004 @11:30AM (#10139354) Homepage
    >> How else would be understand a sentence like "The boy ate a ham___er" (with a few letters obscured)?

    What a way to prove your point. I kept thinking "hamster", "hammer" and then eventually realised that I didn't spot your miss-spelling of 'we' and that I read right over it and filled in the blank.

    Wow. Not only did I do what you did, but not-even-reading your post, I picked out "ham___er", "hamster", "hammer", and "we", and tried to figure out if you were suggesting that "we" fit in the missing space, and he meant to say "hamweer".

  • by cmpalmer ( 234347 ) on Thursday September 02, 2004 @12:19PM (#10140031) Homepage
    I read really fast. I also read quite a bit of fantasy and science fiction. I have noticed the effect that weird alien and fantasy names (N'kalogh or Xyztle) are like driving over speedbumps. The higher the density of unfamiliar and nearly unpronounceable names, the more likely I am not to finish the book (or even pick it up).

    "N'kalogh leapt onto his mighty huyloch and rode across the plains of V'looth'u". Next please.

    This paper gives a convincing pyschological model about why this occurs and it is pretty much what I had surmised on my own.

    So, from now on, please name all of your aliens Bob, Larry, Bubba, or Charles.
  • by TheLink ( 130905 ) on Thursday September 02, 2004 @12:21PM (#10140067) Journal
    Here's one thing you might want to try if you do that. Get someone to track when you blink whilst reading and how often you blink, and whether it's consistent for a particular person, and compare it with other people.

    It seems if you don't blink whilst reading it's like trying to eat food in big chunks... At least for some people. Then again it may be the stress of keeping your eyes open distracting you from reading?

    My postulate is that the brain takes the blink time to dedicate more resources to processing and understanding what is read.

    Coz it's amazing how much "brain CPU" vision/sight takes up for most people. I've got people (kids + adults) to try to do certain coordination tricks - like drawing a circle with the right hand whilst drawing a square with the right foot, or doing an OK sign with the left hand palm facing upwards, L sign with index and thumb of right hand, palm facing downwards, and then rolling hands over - switching to L with left palm down and and OK sign with right palm up, and back again.

    I find that most people find it easier to learn how to do such stuff if they have their eyes closed and visualize it whilst doing it. Once they get it, they can do it with their eyes open.

    Unfortunately many tasks that require high coordination require your eyes to be open :).

    There seems to be a "brain state" difference between having my eyes open or closed. I find it harder to stand and balance on one foot with my eyes closed compared to with my eyes open EVEN THOUGH it is totally dark and my eyesight is useless, or I am blindfolded. (Of course it is much easier with my eyes open and the surroundings visible :) ).

    I am not a scientist, and I haven't done a formal study on these items. So it's just anecdotal, but feel free to go do one - would be good if the resulting study is published somewhere on the internet.
  • by alanxyzzy ( 666696 ) on Thursday September 02, 2004 @12:41PM (#10140318)
    why has English since then been stealing words from other languages like a slum rat during a riot in a shopping mall?
    "The problem with defending the purity of the English language is that English is about as pure as a cribhouse whore. We don't just borrow words; on occasion, English has pursued other languages down alleyways to beat them unconscious and rifle their pockets for new vocabulary."

    - James D. Nicoll
  • Re:I love how (Score:3, Interesting)

    by Colazar ( 707548 ) on Thursday September 02, 2004 @01:42PM (#10141052)
    In German, in certain situations, the verb moves to the end. Moreover, certain verbs get even split in certain situations.

    This actually happens in English, too, but we've been trained not to think of it that way.

    * I'd like to hang up that picture.

    * I don't know where to hang that picture up.

    * His friends are going to move out at the end of the month.

    * Is he going to help move his friends out?

    Most of the time when you are "ending a sentence with a preposition," you are actually doing no such thing--you are using a seperable verb. But because we write them as two separate words even when they are next to each other, we don't really think of them as being that closely related anymore. Also the fact that those "particles" (the technical term for them) look and sound exactly like prepositions helped lead to the confusion.

    I remember in my introductory syntax class, we spent about a week proving that the sentence structures for English and German were virtually identical, but mirror images of each other. (things that German tended to move to the back, English tended to move to the front, and vice versa) but we had to diagram an awful lot of sentences to get to that point.

  • by Smallpond ( 221300 ) on Thursday September 02, 2004 @05:36PM (#10143528) Homepage Journal
    That gives me an even better idea. Its probably much easier to detect when someone blinks then to track eye motion. So just change a few words of text whenever they blink. I suspect the result could be pretty funny.

    As for why people blink at a specific rate, and whether that changes based on level of concentration, that's been studied.

    "Studies have measured the blink rate and tearing on computer workers and noted that the blink rate dropped very significantly during work at a computer compared to before and after work. There was no significant change in tearing. The data support the fact that blink rate decreases during computer use, but also show that other tasks can decrease the blink rate. [cvconsulting.com]

    Possible explanations for the decreased blink rate include concentration on the task or a relatively limited range of eye movements. Although both book reading and computer work result in significantly decreased blink rates, a difference between them is that computer work usually requires a higher gaze angle, resulting in an increased rate of tear evaporation. Since the main route of tear elimination is through evaporation and the amount of evaporation roughly relates to eye opening, the higher gaze angle when viewing a computer screen results in faster tear loss. It is also likely that the higher gaze angle results in a greater percentage of blinks that are incomplete. It has been suggested that incomplete blinks are not effective because the tear layer being replenished is 'defective' and not a full tear layer."

    Which suggests that my blink rate may go up now that I have bifocals, since I have to look through the bottom of them for close-up work (lower gaze angle). I think a lot of the dry eye that I get is from the a/c, anyway.

God helps them that themselves. -- Benjamin Franklin, "Poor Richard's Almanac"