Hack Your Brain: The McCollough Effect

There is a fascinating brain reaction known as the McCollough Effect which is like side-loading malicious code through your eyeballs. Although this looks and smells like an optical illusion, the science would argue otherwise. What Celeste McCollough observed in 1965 can be described as a contingent aftereffect although we refer to this as “The McCollough Effect” due to McCollough being the first to recognize this phenomena. It’s something that can’t be unseen… sometimes affecting your vision for months!

I am not suggesting that you experience the McCollough Effect yourself. We’ll look at the phenomena of the McCollough Effect, and it can be understood without subjecting yourself to it. If you must experience the McCollough Effect you do so at your own risk (here it is presented as a video). But read on to understand what is happening before you take the plunge.

McCollough’s article Color Adaptation of Edge-Detectors in the Human Visual System was written while she was part of the department of Psychology at Oberlin College in Ohio. She went on to many different color research programs — most recently at the University of Dayton Research Institute in Dayton, Ohio. In the 1990’s she changed her name to Dr. Celeste McCollough Howard but I will omit Howard in the rest of the article to keep the period specific references easy to follow. She has now been retired since 2003.

The effect laid out in her paper involves patterns of horizontal and vertical bars. First a subject stares at black and white patterns. Then alternating patterns of horizontal red and black bars and a set of vertical green and black bars (called adaptation). This causes a bit in your brain to be set. The result of this is the ability to detect these patterns and indicate the detection of one of the adapted patterns by seeing its complimentary color. Where there is only black and white the brain now sees black and light green, or black and pink.

Image Credit: Scholarpedia
Image Credit: Scholarpedia

This image shows the sets of horizontal and vertical bars, the center column labeled “adapt” contains the two variations of the bars with complimentary colors (red and green) which is how you would set the bit as I described above. Once this process has gone on for a few minutes (2 to 4 minutes seems to be the average time required) you can then look at the set of images on the left for the magic to happen. The resulting effect is simulated by the color overlay in the far right column labeled “post-adapt”.

At first this seems like your run of the mill visual aftereffect or optical illusion, which is fair enough since we have been participating in these fun optical illusions from a young age. The differences between the ordinary optical illusions and The McCollough Effect are more than meets the eye.

Color Afterimage vs Contingent Aftereffect

As a child I remember conducting optical experiments in elementary classrooms, although it wasn’t until many years later that I referred to them in that way. At the time, they were simply “Cool tricks that Mrs. Badcrumble showed me!” and I’m almost certain we didn’t get into the analysis of that data beyond the explanation of complimentary colors. The most memorable version of this was a color afterimage of the American flag.

Color Afterimage — Retinal

If you take a black surface like a dinner table and place a white circle, perhaps a saucer on that surface and stare at the saucer for several minutes you can probably guess what you will see when you look up at the white wall. That’s right, a giraffe doing pull-ups. Wait, that’s different thing. The white wall should should have a black circle, this is commonly referred to as a color afterimage. The same effect can be done with a variety of colored shapes on light or dark backgrounds. There is a similar principle behind the American flag example I mentioned before. Stare at the center of this mis-colored flag for 30 seconds, then stare at the white area next to it. You should see the appropriate red, white, and blue coloration.

Image Credit: Exploratorium

The above experiment is an example of color afterimage. The colors we see in the white space after staring at the flag are a result of the rods and cones in our retinas becoming fatigued from prolonged exposure to the same color. This lasts from a few seconds to a minute as the eye recovers rather quickly in the absence of constant exposure.

Contingent Aftereffect — Visual Cortex

The concept of a contingent aftereffect is a little more complicated than the color afterimage. Although the name for the concept is fairly straight forward:

  • Aftereffect: Rather than an afterimage there is an aftereffect which could be one of two colors.
  • Contingent: The color that is seen is contingent on the orientation of the lines being viewed, the orientation of the lines is determined by built-in edge-detection of the human visual system (hence the title of Dr. McCollough’s article).

There is quite a bit of evidence that suggests the McCollough Effect (ME) takes place in the brain and is not merely a result of fatigued rods and cones in the retina. There has been quite a bit of work to determine where the ME takes place in the brain, some of which is listed below and can be found on the ME scholarpedia page of which Dr. McCollough is the curator.

The McCollough Effect is thought to involve the monocular pathways at an early stage of the visual cortex. This is based on multiple theories which include evidence provided by other published works. One of the more interesting of these is that the ME can be generated with images that alternate at frequencies up to 50Hz, which is too fast to consciously perceive the color and orientation relationships. The ability to generate the ME at this frequency are consistent with properties of the early cortical areas, which include the primary visual cortex (V1).

The ME can last for much longer than color afterimage when exposed to the adaptation images for the same length of time. The ME has lasted 3.5 months in extreme cases, however a modest exposure to the ME adaptation images of only a few minutes can have a lasting ME of 24 hours or more.

Orientation RecognitionTHUMB_CROP

The lasting ME has some interesting properties in regard to orientation. Not only does the ME represent horizontal lines as one color and vertical as another, the ME has limitations to the angle at which lines are acknowledged as vertical or horizontal. If you were to adapt yourself to the ME (again, I’m not suggesting that you do this… but if you did, this might happen) and then look at the image to the right you would see red in the top left and bottom right quadrants and green in the top right and bottom left. This is the result we expected based on what we have learned about the ME thus far.

However if you were to rotate the image (or your head depending on your hardware setup) you would notice that when the lines rotate to 45º the color overlays are no longer seen. If you keep rotating the image (or head) to 90º you will see the color overlays return, however they are now representative of the line’s current orientation which is not the same color as they were before we started rotating things.

Going Forward

This topic includes a chasm of intellectual publications from academia and private researchers alike. If you want to read a bit about how brain chemistry, brain electricity, primary sensory processes, associative learning, classical conditioning, and sensory adaptation are a part of perceptual plasticity, download this article from Boston University (PDF) to get your beak wet.

The McCollough Effect has interesting properties that are still not well understood. I certainly don’t have a deep enough understanding of the concept to pose some deep final thought sort of questions. What does come to my mind is machine vision. Perhaps knowing more about how our brains interpret phenomenon like ME can help improve color recognition, edge-detection, and orientation in machine vision. What do you think? Let us know in the comments below.

81 thoughts on “Hack Your Brain: The McCollough Effect

    1. Here’s another article, Hackaday: write up what happens if you put your left hand in a bowl of hot water, your right hand in a bowl of cold water, and then put them both in a bowl of lukewarm water. Same kettle of fish.

      1. NO! That’s the point of the article. This is about neural adaptation, NOT aftereffect.

        This is a very real brain hack, and one of only a half-dozen known such effects that can leave “sticky” adaptations that stay in your visual cortex from hours to even months.

        There is one, however, for about 1/3rd of the population involving synesthetic taste + vision. It is not known why it works, and the mechanism of neural adaptation is still being explored by a number of scientists. The first to crack the process completely, may lead to a Nobel prize.

        Look at a deeply saturated color source such as an array of bright blue LED. ( 8×8 neopixels, set to blue, will do it ) Now, place a strongly flavored and scented candy in your mouth. An Altoid works. Look at the light for a minute or so, while enjoying the strong mint.

        Wait 30 minutes.. then look at the bright blue light source. About 1/3rd of the population will report a strong “minty” taste at the same time. This adaptation and habituation only takes one or two sessions, and ALSO lasts days, even weeks ( some people have reported months )

        1. after a, hmm, few, hmm, ‘shrooms and “Dutch travel passes” I managed to “reprogram” mah brain to “see”, in particular, spinning things a tad differently.
          I had noticed that if I took the lens off my SLR, opened the film back and looked through the shutter I could see a whole image at 1/1000 second.
          It was “dim”, but as a photographer I figured it should be.
          So I worked on trying to “freeze” or “stop” things like fan blades and car rims, which worked.
          If you write a decent sized, not too many character word on a bit of masking tape, put it on a fan blade, I can usually read it.
          great party trick, except I never figured out how to turn it “off”.
          It’s kinda weird when you keep seeing car wheels “freeze” as they drive by, with fans I’ll find myself keeping them out of my FOV.
          It hasn’t been too dangerous, fans make noise when they spin, big 2 metre fans make lots of noise, so it’s no big deal, getting wasted with friends and catching arrows is a different story! (3 out of 5 isn’t too bad)

          So cautionary tale kids!

          you really can make permanent changes to your firmware!

          1. The human eye’s FPS is not to do with how quickly we can see an image, but how quickly we can see 2 images, one after the other. You couldn’t see 1,000 separate images in a second. But 1000th of a second can let enough light through to trip a few rods and cones.

            The fan thing is a bit strange, might be more to do with you reconstructing an image. Human eyes don’t have a shutter, it’s impossible to take a “snapshot”, the hardware doesn’t work that way.

          2. That’s correct. Air Force did similar tests on pilots in the 50’s and based on what I understood, seeing an image for 1/200th a second was more than enough for a pilot to determine and identify aircrafts. Some where even faster it appears. Another portion involved rapid sequences of photos (I don’t recall what the time frames where) and pilots could identify the various crafts shown (no puppies or kittens here.)

            It basically washes away the arguments that gamers can’t distinguish frame rates over 60. In my youth, if I paid attention, I was able to see frame transitions to about 70 or so. 15fps on computer monitors was just downright unbearable for me. And before that argument starts, I don’t use FL’s in my house.

            As an aside. Most electric lights have a “starburst” or star-like appearance to me. Especially at night. Natural lights such as flames or stars do not. I thought this was normal for years until I mentioned it to my wife. Nothing to do with the OP but since cyberteque went off topic about his eyeballs, I thought I should too.

          3. Oh… the eye doesn’t actually have “FPS”. It’s a pure analog system. The measurement of “frame” perception in profrssional circles is slightly different.

          4. Different forms of visual perception and cognition have different rates with the higher the level of abstraction typically being slower. So you can’t easily put a finger on an average speed of visual perception, particularly when they would also change as your attention shifted.

          5. @Greenaum

            “Human eyes don’t have a shutter, it’s impossible to take a “snapshot”, the hardware doesn’t work that way.”

            You dont have eyelids?
            I feel sad for you

          6. The human eyelid takes about 1/3 of a second to travel. Travel across the iris is obviously less but not by much. A *slow* shutter speed is about 1/10 of a second and is usually much faster. The two also serves radically different roles.

            The human eyelid is more like the lense cap and serves the same role. It can be pushed into service as a crude iris but isn’t very effective. It certainly is not functionally the same as the shutter in a camera. The human iris is more like the aperture.

            The human brain does the “software” processing equivalent to a mechanical shutter. We most certainly can see our eyelids blanking the world out in that 1/3 of a second but our brains “tune” it out. Sequential stills shown in rapid succession is an unnatural aspect of our world. Our brains and eyes had had about a million years to adapt to the surrounding world. “Moving pictures” has only been around for about 160 years or about 3 or 4 generations. Not long enough to introduce enough evolution in the scheme.

          7. I have experienced this same phenomenon without the use of drugs. I often played goalie in hockey and became able to focus in on the ball (ball hockey) itself. I once spun my head in sync with the ball as it was shot fast enough to create ‘hair’ on it. I also saw ‘hair’ on the oblong faces of other players as their faces were stretched out as I spun my head around so fast. We were waiting for the ball to come down the hill behind my net. After waiting for a minute or so, I checked my glove – and physically shook as it was there. I didn’t even feel it hit the glove.

        2. There’s a lot of flaming going on in this thread, so here’s my anecdote to back this up. When I look at the image with the quadrants of stripes, the top right and bottom left ones are faintly green for me. I have previously never heard of this effect and haven’t undergone any formal conditioning, and yet there is a distinct color difference for me simply based on the orientation (and it holds with rotation as well so it is not a screen effect). Going out on a limb here, but my money is on the fact that my job and my field involves a great deal of precision, specifically visual assessment and estimation of various things (graphs of data, instruments, engineering stuff, etc.) If I am able to actually gauge if lines are horizontal with respect to my visual orientation simply based on a color change, then my brain has been effectively hacked. Doubly so because I was never aware of it until now. I’d say that’s pretty cool.

      2. OK, I just did as you said, but when I moved the warm water bowl on my desk, or even when I rotated the bowl 90 degrees around, the temperature didn’t change from before like you claimed it would.

        Pretty crappy trick you have there :/

    2. You’ve futzed around with the inner workings and gotten a result that is far from typical functioning, finally a “hack” that is actually is a hack, not just some trick or shortcut that excites fools who completely lack any creativity.

  1. On a side note, i remember back in the day opticians used to have a rotating square just like that last image you posted. I was never tested with it but I wonder if it was something to do with this effect?

  2. you idiots are seriously messed up

    this is a SCIENCE AND TECHNOLOGY site

    there will be SCIENCE AND TECHNOLOGY articles here

    If you little fuckers dwelling in your parents basement/attic/garage, (if you’re still in your bedroom, I cringe) all the other stuff you found deadly boring/slept through in high school, just leave….

    some of us that are into OTHER things than coding in VB or whatever like this shit

    1. wow.. really?
      Thanks for the interesting view into your mind regarding stereotypes etc. But Hackaday is slowly changing it’s scope from interesting hacks that people have come up with (HACKaday, remember) to “gee look at what interesting thing I found online, although it’s not a hack at all, we’ll just call it a hack”.

      1. nope

        most of the pricks here wouldn’t know a hack if it ran them down with a big yellow school bus

        this is why I don’t share stuff here, the whole
        “that’s not a hack, just a few Sparkfun modules cobbled together and a bit of code I have no clue about”

        A while ago the was a great article with some video of blokes making axe heads, the butt hurt was amazing (shocking?)

        It has gotten to the point where anyone born before 2000 even knows what a “hack” is.

        A huge percentage of the commenters haven’t got a clue

        Some of you think a “hack” is all about taking a “thing” and re-purposing it or something, like turning a roomba into a sexbot.
        It used to be a “hack” was really friggen messy/outrageous/overly complicated build that had gone from a shitload of breadboards (not an RF hack) to a wire wrapped working version, it had been brainstormed, workshopped, built, rebuilt, rethought, rehashed, till it worked.

        Then a bunch of rich kids with way too much time on their hands made the term “hacker” mean a criminal.

        (I had moar rant about, limp wristed mummys boys, ut you already know)

        At the end of the day, if you don’t like articles like this, DON’T FRIGGEN READ THEM!!!

        Surely you pan-dimensional, hyper-intelligent beings that allow us mere mortals to pollute your divine ass-hatness can comprehends such simple thruths??


        that last bit was “AndrewSpeak” for……

        1. okay. There are lots of hacks that are posted which are simple. That’s fine with me. At least someone did something to hack something together, and usually someone pitches in with a comment how things could have been done easier or something. People discuss, people learn. That reminds me of the mailing lists of yore, which I learnt a great deal from. (rec.audio.tubes, rec.guitar.amps)

          The way you dismiss cobbled together projects sounds a bit arrogant. Every beginner starts having only half a clue (or less).

          Your argument “don’t read the article if you don’t like it” is not possible though. Because first you have to read the article to determine if it’s a hack or not. There is no tag saying “#Notahack”.

          Where do you share your stuff? Perhaps that website is more interesting than hackaday.

          ps: I think turning a roomba into a sexbot is a hack, and I would be interested to read about it, as long as I don’t see any genitals.

          1. I didn’t dismiss anything, you missed the point of my ire completely.

            “popular science” ANYTHING is crap, no matter what the media (looking at you OMNI)

            I’ve been “hacking” since the 1960’s!!
            Technologically speaking the world is a great place, just the whole social, political, economic stuff sucks.
            The commentors on this site hate on anything that is trendy or popular, like Arduino for example.

            FFS when people bitch about “lack of code completion”, you really need to wonder, I foot like auto-completion anything!!

            Anyway, whatever, you do you, over there, away from me, I’ll be over here…

            I “share” my stuff on youtube, facebook, photobucket


          2. Have to reply to my own comment because Hackaday doesn’t allow me to reply on yours (presumably because it would be nested too deep).

            Well I must have missed your point then, sorry for that. Anyway, it’s a shame you didn’t post on hackaday about your rover because that project is the sort of thing I am interested in reading about.

        2. @cyberteque: Relax dude, and dial back on the wacky tobakky. Also, it looks like you’re still pretty new here. Take it from an oldster… it’s going to be OK. It’s not all as bad as it seems.

      2. This article is about neurology, which is interesting. Plenty of hackers have tried to mess with their brain. Using devices in ways not intended, taking advantages of weaknesses or features in hardware, is what hacking IS. Feeding in improper inputs and seeing what happens is a big part of it.

        That’s what McCullough did.

      3. So what exactly is your complaint?

        You posted many times in the comments, and generated many replies. Each one of those raises a counter in telling them the article is popular and desired to be here.
        Why do you demand such articles be posted by hackaday then complain when you get your wish?

        Perhaps you should skip undesired articles in order to show hackaday those articles are not wanted instead?

    2. [i]this is a SCIENCE AND TECHNOLOGY site[/i]

      As a general science and technology site, I find HackaDay lacking. At best, it feels like an amateur attempt to mimic Popular Science, at worst it feels like the kids trying to explain technology they don’t actual understand on a computer enthusiast site.

      Personally I prefer to get science and technology news or explanations from other sources, with professional scientists, engineers, or professional technology writers such as New Scientist.

      IMHO what Hackaday does well is write about is hacks, some and has mixed results on writing about amateur or citizen science, and nostalgic / retro-technology. So I don’t want to encourage them to expand their focus beyond what they can do a good job of. They are already plenty of poor-quality science and tech sites, so it would seem to be a risky business move as well.

    3. HAD used to be focused on hacking hardware and firmware and was most definitely not a general science and technology site. It filled a very special niche for those of us who enjoyed creating something new from existing tech or bending consumer tech to our needs. It shouldn’t be a surprise that those of us who came here to share are unhappy with the increasing number of fluff articles like this one that are taking the place of real hacks.

      Unfortunately, along with the content being watered down, the site now seems to be attracting visits from people who don’t know how to have a civil disagreement but have to resort to obscenity and name calling to shout down those with different views.

      I do find one point of your carefully constructed and well argued position compelling. Should this trend at HAD continue, I can, and will, just leave.

      Oh, and since you enjoy this type of thing, may I suggest you check out the entry on psychological projection at Wikipedia. You may find it particularly applicable to your situation.

      1. The standard response to this complaint has been it’s called HACK-a-day, and you get more than one each day. This is not really a fluff piece as it involves ‘hacking’ (actually) your brain, and thoughts on the multi layered detect and decode system our visual processing employs.

        Long story short, these comments are more of a waste of time then the alleged fluff pieces. Keep scrolling.

    1. absolutely
      this is some strange stuff

      think about how we read

      if you hold up a page of text, doesn’t matter what font size, you can read it

      move it to the edges of your vision, without turning your head or moving your eyes, when does it stop being text that has legibility or meaning, and become “black stuff on a bit of paper”?

      It makes you wonder how much processing power happens in our eyes.

      it also brings into doubt the whole rods and cones thing

      1. Pretty sure they’ve observed rods and cones through microscopes. The existing explanation seems good enough for me.

        The edges of vision are covered by low-resolution, monochrome rods, not the sharp, colour-sensing cones in the middle. In particular the fovea, the centre of high-quality vision, which is actually smaller than you’d think from experience. Lots of unconscious eye movements give the illusion of a full high-quality view.

        The brain’s full of tricks that deceive us over what we see. The brain’s also where things like lines and edges are discovered from an image. The processing power doesn’t need to be in the eyes. Eyes are pretty much just cameras. Between eyes and what we “see”, are several sophisticated neural networks, working in concert, to provide an illusion of perception and awareness that actually isn’t there at all.

        That’s why things like this experiment are interesting. It’s hard to pick apart a brain while you’re using it. Little quirks prove useful principles.

        1. It *smells* like the same effect you’d get from training a neural network on a biased set, then giving it unbiased set. The mind is expecting colors that aren’t there you get some sort of negative value out of a neutral input.

    2. I did read the article.. up to half way, and then I got a bit bored. I got bored because I like hack articles, where people actually make stuff, and it’s very interesting to see what choices they made etc. I can learn from those articles.
      Although this article is moderately interesting because it’s weird, it is not a hack in my opinion.
      What is a hack is when someone finds a roundabout way of making a device or application do something it is not intended to do, or perhaps making something new that can do something.

      I realise that it’s easy to say “we’re making the eyes do something that it normally doesn’t do”. Perhaps some people find it interesting, because it’s out of the ordinary. But it is far away from being anything practical.
      Also, I think Hackaday should not publish research by scientists. That’s just a personal opinion. It’s often too far away from being practically applicable.

      There are already lots of popular science websites. I stay away from them. The reason I like Hackaday is that they show people’s personal projects. Now that Hackaday is turning in to a more “popular science” website makes it less interesting to me.

      1. so why not “skip” the friggen article?????

        If it was not worth thoust august attention, why bother with a few paragraph comment???

        come on guys, we have to lift our collective game. This site is supposed to be better!

        live and let live, we can agree to disagree (some of the time)
        butter is better than margerine
        coke is better than pepsi
        Star Trek AND Star Wars are great (but Stargate is the best)

        Boobs, can we at least all agree on boobs????

        1. We can agree on boobs (not a hack though).
          I usually don’t reply, but sometimes I do because I get annoyed when I find out halfway through the article that nobody actually hacked anything together. Which is the reason I go to Hackaday. And then I tell hackaday it’s not a hack.
          I don’t know if it helps at all, I presume not really, since this is not the first time.

          1. seriously??

            boobs are “hacked” all the time!!!

            We can debate the health risks, saline v soy(or other oil), whether to hard (perky) or not is better

            obviously silicone is just right out…

      2. Your reply shows that you didn’t read the article, and in turn your ignorance which invalidates your whiny complaints.

        At least you’re keeping the ‘not a hack’ going, you unoriginal bastard..

        This is a “popular science” article, is it? Can you kindly link me to another site that has covered it RECENTLY?

        1. wow you even went through the trouble of making a specially named account for your reply.

          Popular science doesn’t mean it’s necessarily published elsewhere.

          Anyway, here’s what you asked for, and it even has “Bizarre” in the title:

          Can we go back to discussing real hacks now?

  3. Ok, I don’t know if I got that correctly. But this hack may change how our brains process color. If I’m not saying a bunch of shit. Can this be used to reduce the effects of color blindness? I have red/green deficiency, can I hack my brain to perceive less blue, and then be able to have a more balanced overall color perception?

    1. In this case I don’t think this result won’t lead to a treatment for colorblindness. The reason is that colorblindness is believed to be a result of insufficient differentiation in the spectral response of the red and green sensors in the eye. This effect is instead changing the neural response in one of the early stage of the optical pipeline. But the color information is already lost there, so no further processing can recover the true color.

      Colorblind people already perceive the world with something very similar to this effect in that they inpaint the color based on the texture and context already. This is why it often takes a long time, or a dedicated experiment to discover the color blindness. CB people learn as children to associate the words red and green with objects and textures and never realise that they are descriminating based on something that they aren’t actually observing. So they know that grass is green by the fact that it is grass (you can recognise grass even in black and white photos) and elmo is red (you can reconise elmo from a black and white picture). But if the grass were red, elmo were green, or the crop was close enough that you couldn’t recognise the object, a CB person simply can’t determine which it is. (This is how those dotty numbers work – the colors are carefully chosen to hilite one number by brightness and another by color)

      You will also do this, the blue/white vs black/gold dress is an example of context failng and come people falling back to different color assessments (do they take into account the lighting).

      Having said all of that, these effects give us a way of probing the deeper layers of the optical system, and may lead to many exciting technologies, from snow crash to safer driving.

      1. I’ve never understood why, if CB is constant, there are some things CB folks are not “allowed” to do

        I had a mate, who was first mate on a boat, that told me he would never get captains papers because he was CB.

        How does that work? it’s not like on some tuesdays port nav lights are going to be green for him

        1. IIRC: Nav lights are red on the port side, green on the starboard, so you can determine which side of a ship or aircraft is being seen in the dark. Could lead to dangerous situations, as there is no frame of reference like with traffic lights, in which the light position is consistent so CB drivers can still tell if they’re supposed to stop or go.

          Incidentally, I only remembered the nav light thing because of Star Trek’s adherence to modern naval traditions in that respect.

        2. No, but if he can’t tell red from green, if they’re both sort-of yellow or brown, he’s going to be hindered in his navigation. Bit of a shame, not necessarily life or death, but there’s a lot of accidents that can happen at sea, so it’s best to put safety first. You can always do some other shipboard job if you really want to.

          There are interesting glasses you can get that can compensate for colour blindness. They let through very specific wavelengths of red and green, different enough that colour-blind eyes can distinguish them. For some people they’re a miracle. Experiences vary.

          If you’re colour blind you might want to look up the wavelengths in question, maybe buy some coloured filters, they’re often specified by wavelength. Use a true white light source, IE not a “white” LED. The Sun is obviously good, or an incandescent light bulb, if you can find one.

  4. The warnings seem a bit over the top. It’s not like this is something out of Snow Crash.

    So I watched the video for the full duration. At the end with the black/white bars, I see the OPPOSITE of the McCollough Effect. Vertical is pinkish, horizontal is greenish, both very subtle. Just like several others reported.

    Twenty minutes later, the effect is undiminished.

    I did a screen capture and tested pixel colors in Photoshop to see if someone’s pulling my leg, which came up negative. I also tried removing my glasses, since they cause some color aberrations, and that doesn’t help either.

    Turning my head 45° makes it go away, 90° makes it come back with the same false colors.

    I thought about this for a bit, and came up with a hypothesis. I wear a fairly strong prescription, so there’s some prism effect; and with lenses roughly twice as wide as tall, the amount of the effect differs in the horizontal and vertical axis. It’s something I’m used to and don’t really notice, except under specific conditions (like viewing the spot from a blue laser pointer I have at an angle, which revealed it actually emits both blue and UV lines). Perhaps there’s some bits already permanently flipped in my brain in an attempt to compensate for this.

    I wish they’d displayed the black/white bars at the beginning as well, so that I could have done a before/after comparison. I suspect I would have seen it from the start. If anyone else tries it, consider testing this by skipping to 2:51 first and looking for the effect, then playing back from the beginning. And if you share the result, mention if your vision is natural or corrected.

    1. I confirm it works. I first read through the article and the image with 4 quadrants looked like black and white.
      Then I watched the video and looked at it again, now the quadrants have a slight shade of green a red on them.
      Horizontal quadrants look slightly green, vertical ones look slightly red.
      I’ll look at the quadrants again tomorrow and see if the effect persist.

    2. Yeah, like afterimages, the color should be reversed from what you were seeing in the ME priming images. As for it going away after just 20 minutes, be glad. That’s the hack part of it, or the suggestion of “solve this problem”, because for some people after a 3 minute priming it lasts for months. As Brandon suggested, solving why this happens is something that will probably lead to a Nobel prize.

      Even 20 minutes is a rather long time for simple tricks like after-images. Those fade in seconds to minutes unless they were really bright lights. But for the effect to have been noted in studies to last months . . . there is something going on deeper in the brain. Or in the eye, or where ever our bodies do edge detection. I suspect it would be interesting to do a reg/green/purple/yellow bars in vertical, horizontal, and both diagonals. What effect would that have on a person, and would it some how help in certain activities to see a brighter color when something is aligned or moving in certain directions (color enhanced motion detection!).

      I would volunteer myself first, but I like photography too much to start adding fake colors into my vision.

      1. It hadn’t gone away after 20 minutes, and showed no signs of fading during that time.

        After which I pretty much forgot about it and went about my day. Now about 12 hours later, and after a nap, I checked again. And now it’s completely gone.

        So I guess it was the McCollough Effect after all. Pretty cool!

  5. A real “Hack” would be using this sort of effect to install a cellular automata on the subjects visual cortex, that implemented a universal Turing machine which ran Linux.

  6. Now if you can find something like this to set anything in to long term memory without having to go through a initial rote method you can make every human have an extremely high IQ and functionality. Of course you’d have to repeat a collection of them every x hours, days, weeks or years to maintain them.

  7. What is the name of the effect where you use a bowl of warm water slowly raise the bowl to immerse subject hand and quietly say “We are going to be late, hurry up and finish going to the bathroom.”

  8. Very cool article, keep following your editorial line !
    Personally, I think that machine vision is more likely to help us understand how our brain works, rather than the other way around (You know dissecting and probing a live brain is not very cool…)

  9. You could use this effect to display color pictures on a monochrome screen or B&W printer. Is that not a hack?

    One thing to try is to do the priming with your left eye, and then see if the effect occurs with your right eye. That would (semi-)definitely full out any cause that occurs in your retina rather than your brain.

    I don’t know what will happen: SCIENCE!

    1. Next up, what will happen if you prime your left eye with one color, and the right eye with the other (still using different patterns)
      Or what happens if you prime your eyes with opposite pattern-to-color matching? :P

    2. I had the same idea for the monochrome screen. I’m curious if you could embed pictures or words into an image that could be perceived faster by someone who has been primed than someone who hasn’t. I also wonder if you can prime yourself at 45 degrees to get a total of 4 different colors. Then, what is the smallest size area that will exhibit this phenomenon?

      I wonder if there are other semi-permanent effects that can be imprinted on your brain.

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