[MUSIC]
Hello, my name is Manuel Spectra.
I work at the University of Oxford.
And here I'm sitting with three experts in the field of color vision and
color perception.
Professor Professor Anne Hubbard and Professor David Brainerd.
About three years ago, three and a half years ago, an image of the Internet.
It was a viral image.
It was a picture, a photograph of a dress, and it was quite polarizing.
Anya, do you want to tell us a little bit about the dress?
>> Yes, this dress divided people into two groups.
Those who saw the dress in the photgraph as white and gold, and
those who saw it as blue and black and huge arguments over this.
People claim to be losing friends.
Over this phenomenon.
How could different people look at the same image of the same object and
see it as these radically different colors.
That's a question that excited the vision science community immediately.
One thing we were so thrilled that everyone else suddenly became fascinated
by this phenomenon of color perception and by the striking individual differences in
color perception, which we think reveals the inherent subjectivity of color,
as well as with further study some of the basic mechanisms that the visual system
uses to make color a meaningful aspect of our visual perception.
So one of the most exciting things for
us as well about this photograph is that although people
looked at the photograph and saw the dresses, different colors in the image.
It's also the case that in the real world, the real original dress,
put under slightly ambiguous lighting can evoke the same controversy.
People looking at this same object but
under ambiguous lighting will perceive it as being different colors.
>> But I think it's worth saying that, if you were to put the dress on and
just walk around, day to day, everybody would agree it was a blue and black dress.
You have to go to some work [CROSSTALK] And fuss around to create this effect.
And that actually, some ways tells us how well vision works most of the time.
>> Exactly.
>> Which is the thing that made it so
surprising when people were seeing the image or the real dress.
>> It's so interesting people say what is it really?
But the question they're really asking is what does it really look like
under natural broadband roughly white light?
Because it's not what it is really.
It has reflectants properties, which can reflect different light depending
on the light that's shining on it and the context in which it is seen.
And the visuals has been constantly trying to resolve that ambiguity
between >> And
it usually does it in an almost perfect way where basically we're happy to call
objects of different color names like a blue top or a brown jacket.
>> Brown, that's great.
>> No, it's not great.
>> [LAUGH] >> Exactly right.
>> Yeah, there are minor differences.
But overall, we doing a really good, great job and
we're not aware that the color isn't really a property of the object.
Because the light that gets into the eyes is the combination
of the reflecting properties of the objects and the illumination and
the illumination changes throughout the day.
And as we enter the room.
>> What you can see here from this little demo is that the light
on the dress constantly changing in color is causing the light reflected from
the dress to constantly change.
>> So you mentioned color constancy or constancy here.
Can you unpack what that term means and
how important it is in basically visual processing?
>> Well, we think of vision is serving a purpose and telling us what is where.
What's out there.
And where is it so that we can interact with it?
And one of the things color constancy does is enable us to use color as a meaningful,
reliable cue to what an object is.
So the colors we perceive objects to be correspond pretty
invariably to their actual reflectance properties, which tell us something about
their material properties, and therefore tells us something about what they are.
But that set of processes is actually very complex and happens on multiple levels.
We're just unconscious of it.
We need to get rid of the contaminating effects of the illumination spectrum
effectively, and get something closer to the actual reflecting
physical properties of the object.
>> But that's not a stimulus that we ever see, right?
We never perceive the reflectants of an object, right?
So it's not in a sense contaminated signal,[CROSS TALK]
it is the only signal that we have.
>> The true is that the reflectance the dress itself doesn't jump into our eyes,
not the physical object interacts with the retina.
It's the light reflected from the object.
And that light brings the information about the properties of the object
the dress, its color, its size and shape its texture.
To our eyes, but it brings it in a form that contaminates, as I may say,
that's contaminated or intermixed with other things, like what
is the spectrum of the illumination and how is it rotated with respect to us.
And I'd say it's worth saying, and this is mostly about color, but
it's worth saying that these issues arise with all aspects of perception the size
of an image on our retina changes with its distance, and yet we don't see
the dress growing and shrinking as we move closer or further from it.
And all that's the work of our brain
delivering to us percepts that are useful about the world.
>> Vision isn't passive process.
We don't just see what's out there.
Were constantly actively constructing hypothesis about what's out there
from the inherently ambiguous light signals that the eye receives.
>> So what specifically was ambiguous then
in particular about the photograph of the dress?
>> Well, it wasn't obvious because there weren't very many
cues the photograph as to what the color of the light source was on the dress,
and it's highly likely that there were actually two different light sources on
the dress, a bluish daylight and a yellowish, probably artificial light.
And this meant that when people's inherent color constancy mechanisms
effectively corrected for the color of the light, that could go one way or the other.
And in fact, subsequent experiments have shown that people who
effectively assumed that the light shining on the dress was a sort of dim
blue light saw the dresses white and gold, and those people who effectively assumed
unconsciously that the light shining and the dress was a bright yellow.
They reported it to be blue and black.
So those perceptions that people reported actually give us
access into the internal workings of their color constancy mechanisms.
>> But you know, I would say that, I think I agree with your conclusion, but
I'll say that, when this phenomenon first came about,
the thought process, at least that I started to go through was
not immediately to jump to that conclusion, but rather to ask,
well here is a case where people are reporting different colors.
What is it we know about color vision?
And the way that light is encoded might or might not explain that.
What would you wanna rule out?
Because most of the time we go through lights agreeing about colors and
something was different here.
And so I think it's worth talking a little bit about what we know about
the encoding of light by the retina.
Is that the same across people?
And what other factors one ruled out before one sort of got this idea about
color constancy in the dress, which I think is now the best idea we have.
>> One of the very first things was of course, the idea that people would look at
this image of the dress, just on different display devices.
>> Mm-hm. >> Yeah.
>> Which would differently calibrate it, and that would lead to differences.
But that could mean extruding it.
>> I remember clicking my phone and rotating it.
>> Yes, yes. >> You could change it
from blue/black to white/gold.
>> Yeah.
>> Because the display had an angular effect.
>> Yeah, and there was some notion, as well,
that it might be a difference between old people and
young people, people who had a bit more, maybe cataract, than young people.
>> So it was- >> Or a difference of
viewing it in artificial light versus daylight.
>> So one of the first thing that happened actually were reports on the internet that
somebody in vision science put one up on a projector and got 15 people to come in
look at the same image and the same display from the same angle.
And they still were fighting with each other about it.
>> [LAUGH] >> So, you know, that was, you know,
good tool out a potential just display artifact.
>> Or was it just a difference in naming?
Everybody was actually seeing the same thing, but some people
call bluish whites blue and other people call bluish whites white perhaps.
>> So that's when we got a couple of observers into the lab and
actually had them do color matches to the dress under controlled conditions, and
we still found a difference.
So that's a good,
that supports the idea that they really perceived the dress to be different.
>> It wasn't just a difference in the way they choose to name something that they
[CROSSTALK] >> And
actually it would've been really surprising.
That report was I remember one of the earlier reports and very important.
But it would've been really surprising if it had been different just because
there have been lots of studies of color naming of little well controled chips and
isolation.
And you know,
the whole paint industry relies on the fact that we can look at paint chips and
agree about their names and develop a nomenclature that people agree on.
So, it had just been naming your it would have been a mystery
as to why suddenly with the dress where the names going differently.
>> But there are cases in which this is the same color will be named
in different ways by different people right?
>> Subtly, yeah.
>> Differences for
certain color combinations like the blue green turquoise.
Some people use the turquoise category as a stoned or between the.
Blue and purple there.
There are different light differences between people for
all the other categories I've seen, they agree really quite a lot.
>> Well the interesting thing is that blue is actually a huge category so especially
in Western cultures, light blues, mid blues and dark blues all coalesce into one
big, big category whereas in other cultures for example, in Russian, they're
divided into two very distinct categories with different color terms for them.
But those other sort of smaller categories, the reds, oranges, browns,
yellows, they tend to be more consistently categorized.
>> And also those are colors that when make people make some way
already judgments.
It's pushing a boundary around blue, green.
Everybody agrees that blue is similar to green, someone's a little blue or
a little greener in their naming.
It isn't the cause of fistfights.
The way, that the way that the it's not true of the disagreements about the dress
color, they weren't just.
The boundary of colors that were similar to begin with.
>> White and gold sounds radically different from blue and black, and
that was one of the reasons why that caused such conflict.
If you really dig into it you find that actually whitish blues are difficult
to classify and a lot of people do put them into different categories,
and blue-ish white can be called a blue or white.
And in fact in Western cultures,
most people tend to think of their whites as being slightly bluish.
It's an interesting- >> But golds and blacks?
>> Golds and blacks, and that's another very interesting.
And again, if you look at the dress, the lace, the black lace is quite shiny.
When a yellowish light shines on it, you get yellow highlights.
That sort of dark color can start to look like a sort of dark gold.
>> Mm hm >> So it's actually not that far away,
a gold and a black.
But that's digging into it and getting into very sort of knit picky details it.
The fundamental phenomenon is that color perception is subjective but
relates to objective physical properties.
>> So there's an interesting aspect here which is that sort of obviously you can
have, say a surface that's painted black or
a matte wall is painted blue in some way.
But gold,
the use of the term gold points to another aspect I think of the dress which is,
it's not just about reflectance is about more complex material properties as well.
So where, in the field of vision science clearly,
we have ways to study material perception as well.
And in a sense, a lot of the work that has been done on
color vision is relevant for material perception as well.
So I was wondering if there's sort of, where do we stand with thinking about
how we perceive complex materials in the world?
>> Well, the color is just one aspect of the material properties of objects and
we picked that up from the reflected light signal, but
we can pick up many other properties about objects from that reflected light signal.
The way it changes with viewpoint tells us whether that surface is glossy or mat.
The way it changes with respect to other objects in the scene tells us
whether the object is transparent or translucent or opaque.
We have luster as well we have metallic versus non metallic reflection.
All of these things can be gleaned from the light signal and
the actual body reflectance of the object which is what we associate with its color,
is just one of those physical properties, >> You know but, go ahead.
>> Perception of material properties is really an emerging research field and
during the last decade.
I mean we've learned that our visual system is capable of extracting enormous
lot of different properties from the input signal like whether surface is smooth,
or rough, or whether it's hard or even whether it's hard or soft.
I mean we learn these associations and we use certain
properties of the inputs even certain queues that we don't even know yet
we're in the process of finding out which ones they are to extract these
very complex properties of the world.
>> I was gonna go the other way though.
Talk about not about not about high level what I would call higher and
mid level visual aspects and complexities, but
actually about the basic encoding of light and something that I think
makes the color differences the dress surprising is we know among most people,
the actual cells that encode the light and MCI this first step of the signal that
gets to us are actually in common among most people so called color normal.
Vision which has maybe 95, maybe more than that 98% of us.
And the fact that that encoding is highly similar means that things like
the way that the colors get mixed on your TV's like the red, green and
blue primaries to make yellow is something we all agree on.
You don't have to have your television customized.
For each observer, because the way their color mixing behavior and
perception works differs.
And so that's one of the things I think, again, that suggests the commonality to
color perception that makes the dress quite surprising.
And again, as that phenomenon first came out I think people scratched
their head and said, well could it be that maybe this particular stimulus
is just on the edge of some normal cover difference.
But I think the evidence now was accumulated from larger studies that
that's not what's going on.
But again, one could imagine those kinds of things and I think many of us did.
>> Yes, so the dress isn't due to some differences in the eye.
>> Right.
>> In the actual receptors, the- >> Correct, yeah.
>> The light sensors that are receiving the light signal.
Or in, for example, the optics of the eye,
in a certain cloudiness of the lens in some people versus other people.
>> Right. >> Completely agree with you,
very important to rule those things out.
But then of course you do have the roughly 8% of males who
do have differences in the light senses.
>> Right. >> In their eye.
>> Right. >> People with color vision deficiency.
And that's another really hugely important source of individual differences which
I think possibly doesn't receive enough attention in society.
And should be receiving even more now that we use colors so
much more for all of our various displace and
devices that colors becoming ever more rampant, I could say.
They say. [LAUGH]
>> Stop, stop because they're small.
>> I mean, the democratic influence basically have the problem that we had
with the dress all the time.
>> Yes. >> I mean, just like a whole dimension of
the color representation.
And when we talk about red or
green, they don't know what we're talking about most of the time.
So, but somehow they seem to cope.
>> Well that's the astonishing thing.
I think that there is an advantage of green rather.
Crotchety old ophthalmologist in the early 20th century said that you had to really
watch colorblind observers because they were very
devious and- >> [LAUGH]
>> He said they were basically-
>> Trained from a young age.
>> Yeah, trained from a young age to learn how to give the right answer and
they were actually super intelligent because they go through life.
Seeing the world completely differently from other people, but
somehow keep this hidden.
I think it was possibly easier then.
And I am concerned now that kids in schools who
are exposed to increasing amounts of color coding will be,
in some ways more disadvantaged by their color vision deficiency,
their inability to discriminate reds, from greens and browns from khakis.
>> But so in the past apart from this idea that there's people who will say lack one
specific photo pigment, there's also variation, natural variation or
individual differences between people who would normally be classified as color
normal observers.
Yet at the same time, we they don't,
I mean it's not as significant, perhaps, in terms of color reproduction.
>> Well, these things, they come in degrees, and
there's a small variation amongst when you look at the little plates and
you read the number off or trace the shape.
That classifies people as color normal, and there's a small variation there.
But there is also maybe this is what you're referring to is cover anomalous
individuals who are not colorblind,
we might say their color different, and whose precepts again won't match
the majority of the populations in the 8% of mainly males that I mentioned.
So that's another source of individual variation, I think is well understood,
not related to color consistency directly [be]cause it's at the visual front end.
>> I think it's quite amazing how the visual system calibrates
itself into the world.
There's enormous variation in the relative number of L and M cones, or red and
green cones that we have in the retina.
And still, when people are asked, as David has shown us very nicely, to adjust
a unit yellow, to mix a yellow out of red and green, they all agree perfectly well.
And I think that's truly amazing.
>> It is astonishing, and
I think we still don't really understand how that comes about.
How that calibration of a visual system comes about.
I mean clearly there's an earlier experience, there's an environmental
influence, and there's learning, but what is it that enables one
person's unique yellow to match another person's unique yellow, despite really big
differences in the way their light sensors are laid out in the back of the retina?
I agree with you.
I think that's a fascinating and unexplained phenomenon.
>> I think it seems like there's a lot of research that could be done in that area,
absolutely.
Now, this sort of circles back to the dress, but there's the obvious question,
well, to a color-deficient observer, have there been any studies looking at color
naming of the dress in people's color vision deficiencies?
>> Only anecdotally, to my knowledge.
>> [LAUGH] >> Interestingly,
some people with color vision deficiency distance themselves from the phenomenon,
don't engage in the debate.
>> They're already used to people telling them.
>> They're so used to that already.
>> [LAUGH] >> So I suppose one of the some
interesting questions for me as an early career researcher in this field is sort of
to hear from obviously more senior people such as you
episode where you see the field going, seeing the next ten to 20 years, and
what the big sort of emerging topics we heard material perception was one of them.
But what's so
where are we heading with color science or the neuroscience of color vision.
>> I think it's heading into different directions.
Of course, there is many more really interesting questions in the retina
that people are starting to look into now using very complex and
fancy new technology like adaptive optics.
But it's also, we're more capable now of studying color vision in the real world or
in virtual realities where we can vary the illuminant as we wish I
think that opens up a lot of new possibilities.
>> I want to second actually, both of the things you said but particularly,
you know, something that emphasized by the phenomenal address is that in a complex
image, I should maybe I should back up and say a lot of what we know about color
vision is knowledge obtained where people looked at very well controlled flat,
spatially uniform discs and maybe a background and if you were really doing
a complicated experiment, the color of the background would change.
That was a radical maneuver.
You get to the dress and now it's a very spatially complex image of a real thing.
With material and mixed with color with the color attached to an object and
I'd say our understanding of how color maps out into this complex objects
is in something Anya has emphasized is that
we get most real objects even though we give them a code name they often,
if you look at the individual little bits, there's lots of colors there that somehow,
you grow them together in a way that's not fully understood.
So that direction, I think, is an exciting avenue, one, I'd say,
where quite what the right experiment to do and
the right way to think about it is something we're struggling with.
So there's a risk as the young researcher there's a risk that it might not work out.
But the questions are really interesting.
>> Yeah, yes, so I think to understand how the perception
of object color is integrated with the perception of the object.
And the scene in the world as a whole, in the natural world, in real,
natural behavioral tasks is still a massive goal.
And one which we do have better tools to tackle, including
better computer graphics, so better control over computer generated stimuli,
and better control over real-world stimuli, multi-spectrum light sources.
Specialist imaging equipment.
All these things give us better control over actual stimuli,
which more closely replicate those natural stimuli with which we interact every day.
But I think there's still debate
over the actual function of color in real world object perception.
>> Something I would say, coming back to the dress and
these points is that, you know we have a challenge to with the dress which is there
is this one image that has this striking behavior and people are there was a talk
about the shore in VSS this year, which was another object that had this bicolor.
And people are beginning to work on
synthesizing stimuli that produce these fights.
So you know, maybe making the world worse temporarily.
But when we understand enough about it so that we can create the stimuli and
manipulate, is it gonna be ambiguous or is it not?
Then we really begin to understand what it is that's causing the ambiguity.
At the moment, I think we're still searching for
the detailed clues that will let us figure that out.
>> And conversely again, going back to the dress if you take the real dress.
And make different environmental manipulations and
determine which of those influence people into seeing it the same way.
You can get a better handle on what those key mechanisms are that contribute to
color constancy.
So for example, taking the real dress and putting in blue light and
then yellow light on it, you will get people to disagree.
But if you put it against a yellow background as in Dr.
Verner has shown, you'll push them on the direction of seeing it as blue black.
Or if you just light the edges with the blue light,
you'll push them in the direction and see it in white and gold,
so then we know that background is important and edges are important.
And we can learn then, a bit more about those critical, real word cues
that the human visual system uses in practicing its color constancy.
>> So in summary in a sense it's sort of more experimental
control we can really tease apart [INAUDIBLE] So thank you for
joining me and this discussion was very interesting.
And thanks for watching.