Cognitive Daily

Blogging on Peer-Reviewed ResearchTake a look at this slideshow (QuickTime required). You’ll first see a photo in perfect focus. Then 12 more pictures will flash by, each of them blurred using Photoshop. Finally, the original photo will appear again. Is it the same as before, or slightly blurrier or sharper?

I’ll give the answer after a few readers have had a chance to make a guess in the comments. Most people with normal vision will gradually adapt to blurry photos (though it might take a little longer than I’ve allowed in this movie). Then when they see a photo that’s in focus, it seems too sharp — as if it’s been artificially sharpened like this picture:

i-94d27324079576c6e88127cd637aa7a4-elliot1.jpg

Photos that are slightly out of focus (though not as blurry as the set of blurry photos they adapted to) will seem just right. But what about older individuals, whose eyes are less sensitive to contrast and brightness, and whose visual systems in the brain may also have degraded?

A team led by Sarah Elliott showed sequences similar to the movie above to 10 young adults (average age 25) and 10 older adults (average age 74). Their sequences were much longer (about 2 minutes), and several tests were administered, with blurred, neutral, and sharpened images. At the end of the sequence, the viewers were asked if the properly focused image seemed too blurry or too sharp.

As expected, most viewers who had seen blurry photos throughout the process thought the final image was too sharp. They were shown the blurry photos again, then viewed the test image again — but this time the image had been very slightly blurred (2 percent of the fully blurred amount). Again, viewers were asked if it was too blurry or to sharp. This was repeated until the viewers said the image was too blurry. Then the test image was sharpened again until viewers reversed their opinion. After several reversals, the researchers could determine the point at which a given viewer was neutral — where the image seemed neither too blurry or too sharp. Here are the results:

i-944edfda10d501870da0837a1c180d0b-elliot2.gif

The older adults accepted significantly blurrier images than younger adults. Even when they were originally shown focused photos, their responses were neutral to slightly blurred photos. But this was a systematic bias: it occurred at every level of blurriness/sharpness of the original photos during the adaptation phase. While younger adults accepted blurry images after adapting to blurry images, older adults accepted even blurrier ones. Once the researchers adjusted for this systematic bias, the results for younger and older adults were the same.

So overall, it seems, even as the visual system deteriorates with age, we are able to adapt to these changes remarkably well. From the perspective of the individual, while everything fades a little bit, the differences between the items we perceive remain constant.

Were you able to detect any changes in the “in focus” photo from the movie at the beginning of this post? Let us know in the comments.

Elliott, S.L., Hardy, J.L., Webster, M.A., & Werner, J.S., (2007). Aging and blur adaptation. Journal of Vision, 7(6), 1-9. DOI: 10.1167/7.6.8

Comments

  1. #1 Andrea Grant
    January 17, 2008

    The original image at the end seemed just a hair blurry to me. I’m relatively young (35) but at the end* of a long day staring at my computer I apparently have 75 year old eyes! But my vision is problematic at other times, so this doesn’t surprise me.

    *I’m in Europe, so I’m about to head home.

  2. #2 Khalil A.
    January 17, 2008

    Nope the last picture doesn’t seem at all different to me. But then I’m only 19 and my sight is perfect!

  3. #3 Tim Buchanan
    January 17, 2008

    Knowing that I was going to be asked about a sharpness later on, I focused on a particular area of the photo. At the end, that area did not look as sharp. I’m 44 but also an observant photographer, ans sharpness is something I look at every day.

  4. #4 Mikhail
    January 17, 2008

    a little less sharp as at first…

    But I do have a couple of concerns :)
    – Constant repetition of blurry images in between tests means each trial measures something different. One cannot argue they measure the same effect on the first pass and after 2-3 reversals…
    – I bet there was a different number of reversals for younger and older populations. In other words, older people should arrive at their neutral point faster. This must be controlled for, especially in the light of my first concern.

  5. #5 Susannah
    January 17, 2008

    I’m 65.

    On the first run-through, I saw no difference at all between the first and last photos. I tried several times, with the same results.

    When I paused the video briefly at each photo, the last one was definitely sharper.

    (And the blurred ones started a migraine.)

  6. #6 Dave Munger
    January 17, 2008

    Oh, I’m sorry to hear about the migraine, Susannah. That was my first complaint when I participated in Greta’s doctoral research, almost 20 years ago. I didn’t get a migraine, but it *was* a pretty bad headache.

  7. #7 Dave Briggs
    January 17, 2008

    So overall, it seems, even as the visual system deteriorates with age, we are able to adapt to these changes remarkably well. From the perspective of the individual, while everything fades a little bit, the differences between the items we perceive remain constant.

    I am 55. Right in between the 2 groups. I suffer from eye strain. So much so that I have to turn the computer off for the whole weekend and then do eye focus, ( 2 second on 1 foot away and then 2 seconds of 30 or 40 feet away), exercises for an hour or two over the weekend.
    It has kept me going, but I still have to write in 12 point bold text during the week to keep the strain down.
    I guess the crux of this is to say that you can keep your vision up, but sometimes you have to work at it. If this helps someone I am glad.
    Dave Briggs :~)

  8. #8 Freiddie
    January 17, 2008

    I’m short-sighted, but I can see that there is a deliberate difference between the first image displayed and the last image displayed. (I noticed it first by normal playback, then checked it carefully by moving the slider.) I’m not sure whether you did this intentionally, but the last image is definitely slightly blurred compared to the first one.

  9. #9 Barn Owl
    January 17, 2008

    I’m 46, and the “in focus” photo looked sharper to me the first time through the series (second time as well). It also seemed a wee bit brighter, but perhaps that’s a function of contrast, due to my (erroneous) perception of increased sharpness.

    I think this will be fun to share with my students in medical neuroscience and neurobiology of aging classes. Thanks!

  10. #10 Mark P
    January 17, 2008

    The first and last images looked very close to me. When I can’t honestly say I could tell the difference. However, when I clicked the play button to replay, and the first image appeared immediately after the last one, the first image looked sharper.

    Dave, you appear to be at the place I was a few years ago (I’m 57). I finally admitted that straining to see instead of getting glasses was vain. I now buy cheap reading glasses by the handfull so I can lose them.

  11. #11 aditya
    January 18, 2008

    yeah, like im Buchanan, I’m a graphic artist, so levels of sharpness and blur are something my eyes are trained to see subtleity (sp?) in. I recognized the original as the original unaltered no problem at the end.

    I wonder how i’d have done without advance warning of what to look for.

  12. #12 p
    January 18, 2008

    by contrast, the last image seemed a bit sharper…. but after pausing and comparing the two photos without interruption, the second photo is in fact blurrier! it doesn’t take a trained eye to see the obvious difference

  13. #13 Michael Chermside
    January 18, 2008

    The last image looked slightly blurrier to me — not a difference I’d have noticed if I hadn’t been looking for it. I have no photographic training (and I’m not a particularly observant person).

  14. #14 Arni Asgeirsson
    January 18, 2008

    No difference…

  15. #15 Dave Munger
    January 18, 2008

    The answer:

    The second photo is blurrier.

    It looks like, anecdotally anyway, we have a little confirmation of the effect. Nice when we get those things to work.

  16. #16 Howard Weinberg
    January 18, 2008

    Age 59. For me the second image was sharper. I’m a little near-sighted and have some loss of focus in my right eye due to damage sustained to the optic nerve (result of too long on a heart-lung machine,maybe)I have noticed lots of adaption in my eyes. I read a lot, compute a lot, and every year think my vision is a little worse, but yearly check up says it isn’t. Still, its interesting to see my vision is a little older than my age.

  17. #17 Mikhail
    January 18, 2008

    I must be misunderstanding the effect… The way I understood it is that following the presentation of the blurred pictures people perceive the last one sharper than it is. If that’s the case, we definitely do NOT have confirmation of this, but rather an opposite. Totting up the votes we get: last image is blurrier (7), same (3), sharper (2)…

  18. #18 Alvin
    January 18, 2008

    Also having done a lot of work in photography and graphic art, the blurring of the last photo was immediately noticeable. I’m sure, however, that I would’ve had a bit more trouble if the test were longer and/or the blurred photos were displayed longer (i.e, more time to adapt)

  19. #19 janmarie
    January 19, 2008

    The last one looks the sharpest to me,but only differing slightly from the first photo. I am in my 60’s and an architectural draftsman as well as a keen photographer. I drive my family crazy straightening things.
    My eyesight is almost perfect – hope it lasts!!

  20. #20 Doug Freckelton
    January 20, 2008

    I’m 66. Like Suzanna (#5) I saw no difference on the first run but if I paused on each blurred image the final image seemed sharper. The first image is sharper when I flick between the two without the intervening blurred images. This is more proof that I am no longer 20 years old.

  21. #21 ilan
    February 2, 2008

    No difference i think.

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