It's Surprisingly Hard To Notice When Moving Objects Change

An anonymous reader writes "Scientists at Harvard have found that people are remarkably bad at noticing when moving objects change in brightness, color, size, or shape. In a paper published yesterday (PDF) in Current Biology, the researchers present a new visual illusion that 'causes objects that had once been obviously dynamic to suddenly appear static.' The finding has implications for everything from video game design to the training of pilots."

Comments

Slight of hand

[Anonymous Coward]

I think this was fairly well known (at least intuitively) by magicians. As long as you keep your hands moving, people can't tell what you are doing with them.

Re:Slight of hand

[PopeRatzo]

I think this was fairly well known (at least intuitively) by magicians. As long as you keep your hands moving, people can't tell what you are doing with them.

Sleights of Mind: What the Neuroscience of Magic Reveals about Our Everyday Deceptions by Stephen L. Macknick and Susana Martinez-Conde.

I saw this book at the Bucktown branch of the Chicago Public Library earlier today in the "New Non-fiction" section. I took it out but haven't had the chance to crack it yet. It looks like it speaks directly to your point.

This is from the blurb:

Stephen Macknik and Susana Martinez-Conde, the founders of the exciting new discipline of neuromagic, have convinced some of the world's greatest magicians to allow scientists to study their techniques for tricking the brain. This book is the result of the authors' yearlong, world-wide exploration of magic and how its principles apply to our behavior. Magic tricks fool us because humans have hardwired processes of attention and awareness that are hackable—a good magician uses your mind's own intrinsic properties against you in a form of mental jujitsu.

Now magic can reveal how our brains work in everyday situations. For instance, if you've ever bought an expensive item you'd sworn you'd never buy, the salesperson was probably a master at creating the "illusion of choice," a core technique of magic. The implications of neuromagic go beyond illuminating our behavior; early research points to new approaches for everything from the diagnosis of autism to marketing techniques and education. Sleights of Mind makes neuroscience fun and accessible by unveiling the key connections between magic and the mind.

This isn't all that new

[Monkeedude1212]

Our eyes are trained to do a whole lot of quick thinking and estimates before sending the raw data to our brain. This is one of the many reasons why simply hooking a camera up to the optic nerve doesn't quite produce the desired results - though our brains seem to be super-learning computers able to interact with almost any other kind of Input - Output, given enough time for trial and error.

I imagine our Eyes are trained to generalize the colour it sees and focus on the appearance of motion, because thats usually more important and relevant to survival, and our eyes are just like technology: Limited bandwidth.

You might call it a defect, I might think of it as evolutionary design.

Re:This isn't all that new

[JordanL]

You might call it a defect, I might think of it as evolutionary design.

I call it evolutionary accident through a process of natural selection propagated by random mutations and favorable environmental factors to suppress competing alleles.

Re:This isn't all that new

[Jesus_666]

That depends on what you call a processor. The eyes do a bit of preprocessing - the raw output of the rods and cones isn't fed directly into the optic nerve; intermediate cells inhibit and excite each other, altering the image in-eye. One example of retinal filtering is how Mach bands are created: Lateral inhibition between the cells causes edges to appear more pronounced than they actually are. The brain is not involved.

(Essentially, the more light one cell receives, the more its neighboring cells are inhibited. At an edge between a light and a dark area, a "light" cell close to the edge will receive less inhibition than entirely bright-surrounded cells due to its "dark" neighbors and thus the light side of the edge will be perceived as brighter. Conversely, the "dark" cells closest to the edge will receive stronger inhibition than other "dark" cells due to their "bright" neighbors, causing that side of the edge to appear darker.)

Different kind of change

[pz]

IAAVN (I am a Visual Neuroscientist). It's a compelling illusion. I have not read the original paper, but will speculate nevertheless in true Slashdot fashion. The change that's perceived before the ring rotates is not so much due to the colors changing -- if you pay close attention -- but something that's called apparent motion. The classic example of apparent motion is the sequencing of lights around a movie marquis -- they appear to move, although the lights themselves are not actually moving. In the same way, the static ring has internal apparent motion as the colors change, because your brain is interpreting, for example, one dot turning yellow next to a dot that was previously yellow, as motion of a yellow dot, even though the underlying dots do not move. While apparent motion can be very strong, it is not the same as true motion.

Then, when the ring starts to rock back and forth, there is a true motion signal that swamps the apparent motion. If you pay attention to a given dot while holding your gaze still fixed at the central white point (not as hard as it sounds), you can clearly still see the colors changing.

So without having read the paper, I reserve some skepticism that they have not actually measured what they think they have. Change is still perceptible, but it would seem that real motion interferes with apparent motion.

Re:Different kind of change

[calzones]

I think in this case, when the ring is static, each individual object is a unique entity. Changes matter.

When the ring is in motion, each individual object becomes part of the whole. It is now one ring and we ignore changes occuring to the ring.

This is entirely sensible because when an animal is in motion, we don't care about the muscles rippling, or the feathers ruffling, or the fur shimmering, or the shadows from trees dancing on it. Our survival depends on being able to watch the animal itself as a single unit. So we are hard wired to ignore the micro changes to a single object.

When the ring moves, all the tiny objects join to become a single ring we must track. When it's not moving, we see they are separate objects.

Re:Different kind of change

[suchow]

hi jon, i'm one of the authors of the paper. just thought i'd answer your question about the refresh rate. we used laptop screens that ran at 60 Hz, but the demo works even if you keep the dots motionless and lift up the screen and rock it back and forth. (you can try this yourself if you download the video.) the demo also works on a CRT at 120 Hz. so yes, it the refresh rate was considered and controlled for, and it doesn't seem to matter much. the motion in the youtube and vimeo videos are a bit jerky because they were converted to 30 fps.

Classic magician's trick.

[RyanFenton]

Switching something when it is in the middle of fast movement is the basis of all kinds of slight of hand tricks. There's just a certain state where the mind identifies something just as a blurb of overlapping color, rather than anything processed meaningfully, and you can freely swap it with a similar item without any notice. Mix in basic misdirection, and you can fool almost anyone's expectations. It's also why you kind of have to learn to juggle by feel & pattern rather than just sight - because the hand really does have to be faster than the (mind's ability to process information from the) eye to keep up with the pattern.

Ryan Fenton

Damn Scientists

[flogger]

As a magician, I have known this for years. Dai Vernon, The Professor, explains that concept the scientists just discovered as a simplistic beautiful statement, "A larger action covers (or hides) a smaller action." Science finally catches up to the magicians.. Damn them. :-)

How would squids see this?

[k2backhoe]

The reef squid has the ability to quickly change colors and patterns on it's body, and seems to signal other squids in this fashion (as well as for camouflage). I wonder if they would be fooled by this illusion or if their neural optics are wired very differently than ours. It would be challenging to try to create an objective test that you could do with them.

Environmental Adaptation

[517714]

Maybe if our ancestors had fed on flocks of fast moving chameleons we would be better at this.

Re:News Flash

[Z34107]

"I can even see color with it" ...is this supposed to be odd or something?

Yes, because only the cones in the center of your eye are capable of perceiving color (the rods on the outside perceive only black and white.) Your brain senses everything in the periphery of your vision in black and white, but "fills in" best-guess colors from what your cones perceive directly in front of you.

I remember that from a psychology lecture only because a fellow classmate, like the parent poster, couldn't believe the color in his peripheral vision was an illusion. So, the professor drew an "X" in the middle of the chalkboard and asked him to stare at it without looking away. He then held up a colored note card directly in front of the "X" and asked him to name the color. (Of course, he named it correctly.)

The professor held up another note card, a bit further away from the X, and asked him to say what color that card was. And then he held up the next card, a bit further away from the X than the last one. And he kept holding the cards further and further towards the edge of his field of vision.

After about the fifth card, the kid was convinced that any card the professor held up was either a shade of gray, or the same color as the chalkboard. Once the note cards were in his peripheral vision, he couldn't tell what color they were, and couldn't tell that he couldn't tell what color they were. Great professor.

Re:stupid scientists

[suchow]

hi, stupid scientist #1 here. (i'm one of the authors of the paper.) you're right, it would be nice to have a flash app that lets you change the speed of rotation. sadly, i programmed everything in MATLAB and I don't know flash. (and hey, didn't our overlord already pronounce flash dead?) on that note, if anyone knows flash and wants to program this up into an interactive demo, send me a message, i'm sure we could work something out.

but you're in luck, my friend. the demo works even if you pick up the screen and rock it back and forth, and i have a movie (link below) with no motion. you can loop the video and whirl the computer around all you'd like, at various speeds.

here's the movie.

as an aside, the first experiment in the paper in a speed manipulation. (spoiler alert.) the fast the ring rotates, the slower the dots seem to change.

Re:News Flash

[Jesus_666]

Except that's not what they tried to show. The site demonstrates that when objects are moving relative to your field of view you become less able to discern changes to the objects themselves, whether it's a change in coloration, size or shape. This is not interesting because your peripheral vision is bad - when the objects are stationary it's easy to tell that they are changing - it's interesting because it's a property of human vision that apparently wasn't known yet.

In fact, just try to focus on one of the dots in the videos. Even if you know it's going to move, you know it's going to keep changing color and the dot is in your center of view you still might fall to the illusion (not to mention that other dots nearby also seem to be unchanging even though they're right next to the one you're trying to follow).


It's not about central vs. peripheral sight, it's about how motion and the perception of change interact.

Culture Bias?

[Arterion]

I'd like to see if there's a culture bias to this. Get someone from a very non-westernized culture and ask what they see. They're regularly not fooled by these kinds of "illusions":

Which line is longer:

>----------

Their eyes just aren't trained to see geometry the same way as westerners who are faced with tons of man-made things everyday.

Re:News Flash

[NeutronCowboy]

Uh, did you read the Wikipedia link you posted? "Cone cells are densely packed in the fovea, but gradually become sparser towards the periphery of the retina." They aren't located only in the fovea, but all across the retina. They're merely more densely packed in the fovea than towards the edge. What most likely happened to your classmate is cone bleaching: the longer you stare at a particular image, the more the particular cones bleach their photoreceptors, and the harder it is to figure out the correct color. Depending on what color the chalkboard was, it's quite possible he simply had stared at it for too long.

The retina still perceives color at the edges, it just does so less effectively than if you focus on the center.