Change blindness experiment

Dinotopia artist James Gurney posted this video about a "change blindness" experiment. 75% of the participants didn't notice that the experimenter who bent under a counter was replaced by a different person. Says Gurney: "Here's proof that most of the time we look but don't see." I think Matisse said something to the effect that he didn't really see things unless he was painting them.


  1. This is ridiculous! First of all these two people look like they could be brothers. Also, the blatant misdirection is never addressed. Every time somebody interacts with one of the two, their attention is always drawn away from the face of the person.
    Sign this
    Here is your form
    Go through that door

    The people barely have a chance to actually look at these people in the eye.

    I really expect more from a Harvard experiment.
    For this to be valid, the attention should be drawn to the faces of the men behind the counter, not away.

    1. That is kind of the point of the experiment. Unless average humans make a point in looking at the other they work on assumptions. And one assumption is that things usually stay where they are.

      I’ve seen similar experiment with people on the street, when the participants ask for directions. Some distraction comes a along and they get replaced by another person. Only when the did something drastic like changing the gender of skin color people really started to notice. And quite a few seemed to notice but than adjusted their memory to fit the current situation.

      1. Of course cons depend on this. They also depend heavily on misdirection. I’ve learned a few card tricks in my day, which include blatant switches that anyone with bad vision can see. However I misdirect your attention so that you never notice. Which is what they are doing here.

    2. This is ridiculous! First of all these two people look like they could be brothers.

      They are different persons, different shirts and all. You wouldn’t mistake one with the other if you paid any attention.

      That people don’t look at them in the eye and don’t get a good image of them is kind of the point. The same “misdirection” (sign this form, go there, etc) happens in many situations in real life, and we would still be surprised if we couldn’t tell between two persons because of it.

      “””For this to be valid, the attention should be drawn to the faces of the men behind the counter, not away”””.

      For this to be valid based on your misconception of what the purpose of the experiment is?

      It’s not to prove that we can tell people apart when they tell us: “LOOK, see THIS GUY. OK, now look away. See THIS GUY. ARE THEY THE SAME? ARE THEY?”. It’s to prove that in some situations we are blind to changes in our environment.

      If this can happen with people who GIVE YOU THINGS, STAND NEXT TO YOU and TALK TO YOU, consider what will be the case with changes in surrounding furniture, sings, structure, etc…

  2. This doesn’t surprise me at all. Working in retail, I can tell you that people just don’t pay attention to the people who serve them. Customer will come in asking for an employee who told them something last time, or complaining about an employee, and when you ask who it was or if they can describe the person, they often have no idea. They can give you male or female, and that’s it. I’ve had people come in and say “it was the brown-haired girl with glasses” when none of our female employees wore glasses. People pay attention to whatever they came in for, but they don’t pay attention to their surroundings.

    1. This happened to me in a grocery store a few years back. I went to the counter with two six-packs of beer. The guy in line ahead of me also had two six-packs of the same beer. The total was something like $3.98. He gave the cashier $4. When the cashier turned around to make change, he picked up the beer and walked out, blowing off the two cents. I stepped up with my beer. The cashier turned around, gave me his change and receipt, put my beer in the bag, and said “Have a nice day!”

  3. I find the interpretation of this study highly questionable. The idea that the person at the desk would change is, in normal society, crazy, so it’s not one that we really consider. Since we generally like not to appear crazy, especially in front of psychologists, what’s the chance that even people who had noticed the switch would mention it? They probably just though they were going crazy.

  4. powers of observation are dulled by lack of use. follow status quo may lead to blindness or walking off cliff?

    Laurie Anderson(who can be seen on her own or as wife of Lou Reed) says:

    ‘to be an artist is to be observant.’ and since art is life….

    ‘To find yourself, think for yourself © Socrates 469 BC'(where did I copy this from)

  5. Derren Brown did a similar thing i think – he was talking to randon people on the street, and people would walk between them carrying a portrait of him, or something opaque, when he would switch with someone who looked totally different. Most of the people didn’t notice at all.

  6. See also

    The moral of the story is that your brain is just making stuff up as it goes along, to roughly fit what it roughly sees. If it’s unusual or unexpected, it does not end up in the story. This stuff matters — when you’re on your cell phone driving, your brain is still making stuff up, but it’s a whole lot more like “blah-blah, driving, unh-hunh, driving, yeah, driving”. This is also why cyclists should not ride past pedestrians in a crosswalk, even when there is room — assuming you are wearing the US-standard SEE-ME-SAFETY-YELLOW, you will magic-trick the driver that is fixed on not hitting you, right into the drab pedestrians still in the crosswalk.

  7. @Davidget Thanks for posting the links to those other videos. I’ve always found them an incredible demonstration of this effect.

  8. “powers of observation are dulled by lack of use. follow status quo may lead to blindness or walking off cliff?”

    I don’t really see how this has to be a negative thing. You simply cannot notice every little detail, your brain would shut down from overload. If you actually took the time to notice every little detail and commit it to memory, you could easily spend hours standing around just staring at your surroundings. This frees us to pay attention to concepts instead of forms, and could be seen as a side effect of being able to reason abstractly. I think it’s a worthwhile tradeoff.

    1. Well of course, if one is a fair ways out on the Autistic Spectrum then one does start out spending a lot of time staring at the incredible wealth of detail available. After a period of time, whose length is dependent on the independent variable of one’s IQ, one begins to formulate patterns in the chaos and therefore becomes more active and interactive. A highly sensible improvement on the old scheme from the previous stage of evolution where a simple, static filter is used to get rid of 85-90% of the input based on pre-technological criteria from the African Veldt.

      Still, I often wonder what it would be like to have to deal with that “Old School” level of filtering. I imagine it must be like having a toilet paper tube that you peer out to the world through and that you move around depending one your current top priorities.

  9. Defense attorneys should show this to every jury where “eyewitness” testimony is being used to convict their clients.

  10. A cutesy-poo experiment that proves nothing:

    1) They’re there to sign a document. Their focus is and SHOULD BE on that.

    2) They see the change, but are subconsciously editing it in the context of their main goal (see 1 above) and in terms of not wanting to be involved in whatever games these boys were playing (subconscious: looks like these clowns are bored and want to screw with the customers… ignore it – let’s not get involved in these weird office politics, we have bigger fish to fry today).

    Want to REALLY see if people notice change? Cave in a piece of the ceiling near where they’re standing. They’ll notice.

    These ‘experimenters’ are over-educated in things that don’t matter, and have too much time on their hands.

    1. Mister Snitch is on the right path in a way I think. I’d bet that if you monitor the subject’s heart rate and blood pressure as the switch takes place, they’d go up. The brain knows something has happened, and arousal thus goes up, but the change doesn’t set off any of the unconscious triggers that cause conscious awareness. I bet it sometimes gets even closer to conscious than that; a bit of the brain says “That can’t have just happened,” and the subject rejects the interpretation before even being aware of it. If that’s what happened, I’d bet that the subject will recognize if asked that the encounter made him or her uneasy in some unexplained way.

    2. A cutesy-poo experiment that proves nothing:

      2) They see the change, but are subconsciously editing it in the context of their main goal…

      Wow. Just wow…

      The fact that you think that proving that people are “subconsciously editing” their perceptions and their memories one moment to the next is a “cutesy-poo experiment” that proves nothing shows how little you understand about cognitive science, or perhaps that you randomly dismiss science without really thinking about it.

      This kind of work has huge implications on how our brain processes information before it ever even enters our consciousness. We feel like we are seeing what’s there, but we aren’t. We are seeing a very edited version of what’s there that is filtered by how our brain makes sense of things.

      The idea that you could completely swap two people and have participants not notice, even when they recall looking at the person before and after the swap, shows among other things that you really can’t trust your own memories. In studies, people often rate their confidence of memories like this very high, even when they are completely false and made-up.

      Showing how malleable our memories and perceptions are is not idle science. It really starts to get to the heart of what consciousness is.

  11. If i noticed something like this, I wouldnt react any differnetly. I would think a couple bozos are bored with their job.

  12. I didn’t notice the change in colour of the professor’s shirt until pointed out here.

    But then I didn’t notice that it was red to begin with.

    That’s not change blindness – that’s selective (maybe narrow) focus. How can I notice a change in something I’m not even aware of to begin with?

  13. @ #18 – so how the human mind works doesn’t matter? You’ve made some pretty amazing conclusions there on very little data. It’s not about whether they see the changes. It is about why their brain chooses not to mark the changes on a conscious level, and what implications that could have on a larger scale or in other contexts. The subjects themselves were surprised that they did not notice the change. To say this “proves nothing” is not true at all. Especially when you then go on to excuse exactly what it does prove – that the brain prioritizes incoming data.

    I consider myself to be a very observant person, but I didn’t notice that the professor in the video had a different colored shirt. I also didn’t notice the moon-walking bear in the other link, which was even more of a shock to me, since it is something you would think would stand out. The desire to understand this effect and why it happens is hardly worthless, in my opinion.

  14. Also confirms an experiment from Luis Buñuel called Cet obscur objet du désir.

    I find it curious that the two examples at the end of people who noticed something was up were both women. Was there any difference between the genders?

    I remember reading of another study where they made people sit in a waiting room for five minutes before the study could start, and then answer questions about the contents of that room. In that case, women tested better than men. (Though I certainly hope they controlled for people who brought books with them.)

  15. I agree with the statement regarding misdirection. This experiment -may- elucidate how well people can be misdirected, though.

  16. I have since childhood carefully observed adults as , when a child, I had good reason to know when the situation would blow and you could tell by facial expression. Now as an adult I have a better than average ‘kee’ obserers eye and notice even small changes in a persons face and body language and I certainly saw the change here.But to my everyday surprise the average person does NOT really ‘see’ the other . Which makes me think of how con men etc get away with it!! Watch “Dirty Rotten Scoundrels” with Steve Martin and Michael Caine and LEARN.

  17. You’d have to do more specific testing to control for other factors if you really wanted to see if one sex noticed more. Maybe people tend to notice more if the person is of the opposite sex (or more precisely, if the person is of a sex that they tend to be attracted to). Maybe one sex in this particular location is culturally inclined to pay more attention to looks or fashion than the other. Those are just off the cuff, I’m sure there could be other factors as well. Also, I’m assuming this experiment was conducted on more than the handful of people we saw in the video, they didn’t mention if the breakdown of the examples shown are indicative of the demographics of the two groups. It’s certainly possible, though, I’d be really interested to see the results of such testing.

  18. Some people at UC Berkeley did this same type of experiment a couple of years ago.
    I certainly know I have change blindness, even worse actually. A couple of years ago I was in two different classes with the same guy who was white with brown hair – he was my lab partner in chem. and sat two seats away from me in math, but it took me two weeks to realize it was the same guy.

  19. In my layman’s opinion, we are all wired to pay attention to what is most likely to help us survive.
    We filter out an awful lot of stuff.

    Survival of course is not at issue in this scenario. But our wiring is. And it’s operating at all times.

    A side point: a cat is wired to focus on motion. It will exclude almost everything except what is moving from its consciousness, never mind that what is moving is (say) a flashlight beam or a string and therefore inedible.

  20. Some incredible change-blindness experiments you can perform on yourself:

    Each shows two images, flashing repeatedly one after the other. The images are different in some large, obvious way. Sometimes you’ll see the difference immediately; other times you look at the images in frustration for five minutes knowing there’s a change, swearing there’s no change, and finally seeing it and hitting yourself over the head for how obvious it is.

    1. Wow! Those image pairs (Comment #34) are remarkable! Until I actually foveate on the area of change, I just can’t see any difference at all. And the composition leads the eye away from the area of change, so yeah, it takes forever to find/see the difference.

      Nice one!

  21. A couple other notes: people notice the changes in swapping people most the other person is in-group vs. out-group.

    So a man is more likely to notice when two men swap than when two women swap. A white person is more likely to notice when two white people swap then when two black people swap. An old person is more likely to notice when two old people swap than when two young people swap.

    What’s probably going on is that, when you see a person of, say, a different race, you tend to compartmentalize them as “a person of such-and-such a race,” as opposed to “a person who looks like X.” The race (or age or sex) becomes the only salient characteristic, when it’s not of your race or age or sex.

    This kind of thing influences not only how we figuratively perceive other people who are not in our group, such as stereotyping all X together, but also how we literally perceive them. Two black people really do look more alike to a white person than two a blank person, and visa versa, in the same way that we think two phonetically similar sounds in a different language sound “the same” to us, but completely different to a native speaker.

    (Can anyone tell I wrote my thesis on some of these ideas..?)

  22. There’s an assumption that the person cares about the change. Also, the first guy ducks down while the subject’s attention on them—he’s gone; doing a filing thing…then another guy appears out of ‘left field’..could have been guy #1’s assistant. The subject doesn’t care..they got their form and go on their way.

    1. What, really?

      It’s amazing what lengths people will go to in order to support their personal biases that all scientific studies must be hooey.

      If you saw a person behind a counter that you had been interacting with duck down, and then a completely different person, his assistant perhaps, just popped right up out from under the desk with no explanation and continued the interaction, you are really telling that that you wouldn’t bat an eyelid, because you “got your form and so could be on your way?”

  23. Oh, geez! Now I’m wondering how many times this has happened to me and I didn’t notice! I’ve always suspected this world has been trying to drive me mad and this isn’t helping!!

  24. I just don’t notice things. I could stand two feet from someone at a party for an hour, talking with them, and while I’d remember what we were talking about, I couldn’t pick ’em out of a lineup an hour later – especially if they’d changed clothes. (God help me if the person I’m supposed to notice is in uniform!)

    And this is why when I take my kids to a crowded venue (think Disneyworld), the first thing I do is to take cellphone pictures of them, so I’ll know what they’re wearing. The next thing I do is to get them to point out employees to me, so I’ll know that THEY know whom to find if they get lost. I’m not paranoid about my children; I just know my limitations!

    My parents, in their 60s now and cognitively absolutely sharp, have a similar failing; when they go on trips, they dress in the same clothes (!): khaki pants and denim shirt, jeans and white t-shirt, whatever it is, they’re wearing very similar clothes. So if they get separated, they just have to look down at themselves to know what to look for in the crowd. I laugh, but I admire their creativity…

  25. I agree with sam1148, and I believe you can test whether or not the assumption that the person cares about the change matters. Redo the test with a couple of pretty women who also look similar but different. If the number of men who notice goes up, that will tell you something!

  26. It seems that a lot of people here are commenting without paying much attention to the video. Claims that people would simply not feel comfortable mentioning it are ruled out because the subjects are specifically asked whether or not they noticed anything unusual. Moreover, after being told of the switch, they are then asked again if they noticed.

    Incidentally, the Derren Brown version has some interesting history. This sort of experiment was first done in a setup very similar to Brown’s (with I think moving a large door). However, that was difficult to control and doing it raised issues of experimental consent. Hence this implementation.

    People poo-pooing this experiment don’t appreciate how little understanding we have of how cognitive processes work especially in taking the data we get and putting it into what appears to be a coherent whole. If one didn’t know about this sort of thing, I’m pretty sure that most people would expect the percentage of people who would notice to be far higher. Experiments with cognition and sensory perception frequently show how much we really don’t understand about how even our own brains work.

    Anonymous @31, the two students being the same person sounds more like a context issue rather than a change blindness issue. Didn’t cognitive effect but can also lead to counterintuitive results.

  27. This, by the way, is how one becomes a Master of Disguise. You don’t actually need one of those Mission Impossible latex masks to turn into some Colonel on the other side in order to spring captured members of your team. All you need to do is match six or seven points of comparison to match up with all of the identifying input that’s left after most things are filtered out. Gait is probably the most important.

    Interestingly enough, the more familiar someone is with the object of impersonation the easier it is to initially fool them as they’ve traded speed of recognition for accuracy w.r.t. the most important people around them and so use even fewer points of comparison. This is why spouses of missing persons often can’t provide even the most cursory description of the disappeared person. They often really haven’t seen the other person for years: just looked at them.

    I tested this out once by coming back from a vacation with my first set of contact lens and some glasses frames with the glass punched out. Time and number of interactions until they asked “why don’t your glasses have glass in them?” was inversely proportional to their closeness in the workplace. The receptionist immediately asked. My cubicle-mate of 7 years never asked and was shocked at the end of the day when I put my finger through the empty frame with the tag line “but what is reality anyway?”

  28. This doesn’t seem surprising. The ones who seem to notice are those who look the person in the eye. And based on my personal experience, around 75% of people don’t look you in the eye, or only do very briefly before turning away.

    Repeat this with black belts in karate, or professional dancers, and I bet 100% will notice. Repeat this with a meeting of introverts, and I bet far fewer than 25% will notice.

  29. There’s got to be a limit to this sort of thing. Let’s say Bill Cosby handed you to paper, then Carrot Top popped up afterwords. I bet more people would notice this than two somewhat similar looking guys.

    How many physical differences, I wonder, would it take to get most people to notice?

  30. Servants and old people have always been “invisible,” not really perceived. We just do not see people who of no significance to us.

  31. I agree with a few of the other commenters. Even if I noticed the change, I wouldn’t give a crap enough to even mention it. As long as I got what I was going there for, I wouldn’t say anything.

    Perhaps it’s a personality thing. Maybe extroverts would mention the noticed change whereas introverts wouldn’t. I consider myself an introvert. There are plenty of times, I notice something and just don’t want to bother conversing with someone about it.

    For instance, you ever have someone call you by the wrong name? Like most people, I’ve had that happen on more than one occasion. Unless, I know that I’m going to have to deal with the person that has addressed me incorrectly, for some significant period of time, I almost always don’t bother correcting them. I just don’t want to converse with them really-not beyond anything except for what is necessary.

  32. This is not at all surprising, or even interesting. The differences are pretty subtle if you have no reason to notice them. Except for the shirt colors, verbal descriptions of the two (from memory) would pretty much coincide, even if you paid attention. Seeing the difference side-by-side is a pretty different thing. Few could tell the difference between two similar pitches if separated by other pitches or noise. But the difference would be obvious to almost everyone when played together or one immediately after the other.

    We’re not blind to non-subtle changes, which could easily be demonstrated by using 2 people with different height (4 inches or so), or different race, or different sex.

  33. Person with a cognitive science degree sez: Attention blindness is crazy stuff; the most famous – and silly – experiment on the topic was published under the title “Gorillas in our Midst”. (The stuff @34 references is a better example of actual ‘change blindness’ rather than ‘attention blindness’ – even looking for it, something about the flicker screws with perception.)

    Essentially, they found that when you’re busy paying attention to something else, even things that ought to be FREAKING OBVIOUS – like a dude in a gorilla suit walking through the middle of a basketball game and standing there beating his chest for a minute – can go completely unnoticed. Even when it’s right in front of your face. They specifically had the gorilla guy walk through the middle of the area the people were looking at – no “but they were looking away” argument on this one.

    As best we understand it, attention is like a spotlight in the dark; you can only see what it’s pointed at. I’m probably as keenly aware of these effects as anyone – I know the science on the one hand, and I have an artist’s training in really seeing things on the other – and even then, it only lets me manipulate WHICH things I notice better, not get rid of attention blindness effects to all that large a degree. Apparently there’s just plain too much information out there, and the brain HAS to dump some of it to let us focus on the bits we care about. And yes, the amount of screwy that could be going on in the dark outside our little spotlight is kind of creepy to think about.

    Incidentally, the ability to ignore things we aren’t paying attention to may have something to do with that story about swearing reducing pain, too. The emotional loading on curse words makes them more distracting than neutral ones… using ‘sex’, or some word with particular meaning to you personally, would probably work just as well. And I’d bet that attempting to distract yourself by reciting a bit of poetry or something would work even better, because it requires so much more attention.

  34. Of course. The brain only emulates reality, constructing an internal model (what we actually perceive) based on the input that has various degree of importance to the brain at the time.

    A lot of stuff gets skipped or adjusted. For example, if the light is red in a room, then a banana should look reddish too, because it reflects red light more than it does yellow (simply because hardly any falls on it, to begin with). But our brain adjusts and shows not the absolute color but the difference with the ambient light: the banana looks yellowish to us, even in an almost entirely red light.

    What we perceive is not what’s really out there, but the internal model of it constructed by the brain.

  35. I often cannot identify my waitress or flight attendant even after speaking to them several times. I just don’t look at service people like I do everyone else. The clerk at 7-11 is more like an atm to me than a person.

  36. Some people are more awake to their world… period. Other people are more “people oriented” and would tend to notice the switch. I bet others are looking for potential mates and if so then would notice the switch. I wonder if women noticed the switch more often with men behind the counter and if men would notice more often if women were behind the counter?

  37. One of the explanations for change blindness (and yes, it is a significant and well-researched aspect of the human experience, not just one dumb obvious experiment that you totally wouldn’t be fooled by because you’re wonderful) that I think seems pretty reasonable is the idea that we tend to offload information about the world around us.

    Because our brains “know” that the outside world is for the most part static, they assume that there isn’t any need to construct an exacting image of the world around us. I mean, why do that when you can just look at it whenever you need to refer to it? So what that means is that we can be tricked pretty easily by things that change without providing any sign to really grab our attention and re-work our sketchy internal model. Once they’ve changed we just assume that they must always have been like that, because we lack an accurate comparative model.

  38. This reminds me of the Hitchhikers Guide to the Galaxy book, when the spaceship is hovering over the Cricket stadium but no one sees it because it is “someone else’s problem”. Fascinating how our minds edit what we see.

  39. Some of the commenters here seem to be demonstrating another cognitive limitation, aka i’m-too-lazy-to-read/watch-all-of-it blindness (e.g. comments #2, #37, #50), which I guess is a type of inattentional blindness. The participants WERE ASKED AFTERWARDS if they had noticed anything odd about the sign-up process. Introversion/extroversion and whether you’d register or express some kind of surprise is not part of the study (furthermore, this would be really hard to quantify and would be blasted for not being rigorous enough). The 75% figure comes from asking people whether they had noticed the swap or not. RTFA applies in all situations, whether it’s a video post or an article.

  40. The interviews are good, but the first girl gives the guy kind of a weird look before she leaves, like she noticed something was off. Is it that 75% of people don’t notice, or 75% aren’t secure or brazen enough to speak up about it?

    1. That girl was supposed to be an example of one of the ones who do see.

      “Being brazen enough to speak up about it” has nothing to do with the experiment — did you read #55’s comment above? It’s not testing whether people care enough to comment, or are too shy to comment.

      Anyway, in the more extended version of this video, which I watched a number of years ago in college, I believe that very girl laughs when the researcher starts asking questions about the guy(s): “you mean, did I notice how they swapped places?”

  41. It seems to me that in this particular experiment shown, the people being experimented on had disengaged from the moment and had already shifted their mind to the next task.

Comments are closed.