First off, I would like to just introduce attractiveness a little bit to you.
Especially thinking about
why should we even bother thinking about attractiveness?
Well, first, psychological research has shown that people largely agree
on who is attractive or who is perhaps, less so.
So I'm pretty sure most of you in this room would agree
that Angelina Jolie is perhaps somewhat more attractive than Ugly Betty.
And this perception of attractiveness even hold universally.
So even if you went to a very different culture,
people would probably still agree that Angelina Jolie is more attractive.
In addition to this, work in psychology over the last two decades or so
has shown that attractiveness has advantages
over and above perhaps getting bought a drink in a bar on a night out.
And specifically, these advantages include things
like being seen as more honest, more socially competent,
more successful, more trustworthy, friendlier, and even smarter.
And that last bit is quite important because even in your career,
your attractiveness levels matter.
And this holds by the way for men just as much as for women.
If you are more attractive, you are more likely to have a good career.
Being attractive literally pays.
And we call this the Halo Effect,
which means that simply because you look a certain way,
people make all sorts of attributions about what you're like.
And while that might seem a little bit gloomy for some,
there's actually a flip side to this coin
which is: can you make yourself more attractive?
I'm not talking about going and getting plastic surgery,
or going to a salon and paying for very expensive beauty treatments.
I'm talking ... - oh, not about that! - I'm talking about changing your health.
With that in mind, I'd like to turn to the animal kingdom for a moment.
You can see these beautiful birds on here,
and they have something in common which is that they are all colorful;
and these colours aren't just there for us to think of them as beautiful
But they're actually signals that they use to attract mates.
The more colorful these birds are,
the more likely they are to find another bird
who's willing to mate with them.
And this is important and relevant for humans,
because the colors in these birds are not actually something
they produce from their own biology.
This is something they can only produce following their diet.
They eat something that makes them colorful.
And this something are carotenoids.
Carotenoids are little pigments; they are a group of pigments.
There's about 500 or 600 different ones.
But they have something in common,
which is that they are all red, yellowish, orangey in color,
and they are contained in almost all fruit and vegetables.
Importantly, they are actually contained
not only in carrots that are obviously orange
but even in fruit and vegetables that are perhaps less clearly colorful,
including green vegetables;
and fruit, for that matter.
And these pigments in the birds
signal that these birds are able
to go out and look for a healthy diet
by foraging through perhaps the forest or the fields,
which they couldn't do if they were in poor health condition.
So in those birds, being very colorful suggests to a mate that they are healthy.
Of course, us humans,
don't have to go in to the forest to get fruit and vegetables,
we can walk in to the supermarket and buy any food that we desire.
Our problem is more, perhaps, that we'd choose foods we shouldn't eat.
I'm sure you're all aware that we are supposed to eat
about a third of our diet from fruit and vegetables.
This is also often referred to as the five a day:
you're supposed to at least eat five portions of fruit and vegetables per day.
So if eating fruit and vegetables
- which have all sorts of health benefits
including getting vitamins, getting fiber,
and getting a whole range of relevant products into you body -
if that is important for birds, then what about humans?
Do we perhaps also somehow signal in our appearance
the fact that we have eaten lots of fruit and vegetables?
So, to recap how this works:
the carotenoids that we've consumed with fruit and vegetables
work and function in our immune system.
So if some nasties, some bugs enter your system,
one thing that the immune system can do is use carotenoids
that are stored in our system as antioxidants
that will then fight these nasties and cause them to disappear.
If there are carotenoids left over, as it were,
after this immune function has happened,
these carotenoids can then be layered into our skin.
This happens through a process whereby carotenoids are entered into the sweat
which is then of course sweated out through the sweat glands
and are literally layered onto our skin.
And this layering process causes our skin to turn somewhat goldenish yellow.
This is just a representation; it's not accurate.
You're not going to turn exactly that color,
if you eat more fruit and veg, but it illustrates the point.
There's a different scenario that we could imagine
whereby again, we have plenty of carotenoids,
but this time, there isn't just four of these nasties but many more;
which should hopefully appear on screen in a moment.
There we go.
And in this situation, the majority of our carotenoids stored
might be used up to fight these nasties.
And then, there's very little leftover to go into our skin,
which then causes our skin
to turn a lighter color again.
This is because the carotenoids
that were originally layered into our skin get rubbed off,
and our skin of course rejuvenates all the time.
So if you don't replenish constantly,
then our skin color will change back
to a less attractive version of itself.
That led us to the interesting question
of whether this different skin color is perhaps found attractive in humans.
Remember, in birds, the high-carotenoid coloration
was something they use to attract mates,
which is similar to attractiveness in humans.
And given this is a cue of somehow health, so you have a lot of disease burden,
you might not be able to create this lovely skin color,
this might actually be a cue of your appearance.
So, for this, we conducted an experiment.
We first measured empirically
the axis of color change in skin associated with carotenoids.
To do this, we had a group of students
that eat a lot of fruit and vegetables in their regular diet,
and we measured their skin color;
we also had a group of students
that didn't eat very many fruit and vegetables
- It was more easy to recruit in that group unsurprisingly -
and we match these groups on their sex, on their age,
and on other lifestyle characteristics
so that we could be relatively certain
that the only consistent difference between these groups
was their fruit and vegetable consumption.
After we measured each individual's skin color,
we averaged this skin colors, and could then calculate
the difference between the color of the high carotenoid intake group
and the low carotenoid intake group.
We could derive this kind of color axis.
This allows us to take a photograph of anybody, for example this girl,
or anybody in this room,
and we are then able to transform this image
to become either higher or lower in carotenoid color.
We then asked people, in an experiment
which color they think is more attractive.
So let's try this here: you see the two versions of her face.
Who thinks the girl on the left is more attractive?
One … not many, good.
Who thinks the girl on the right is more attractive?
That's a vast majority,
and this is consistent with what we found in our experiments
where of course we wouldn't present people with only this one girl
but with a large range of faces that we have manipulated in this way.
We find that in fact, nine out of ten people approximately
chose the higher carotenoid version of faces as more attractive.
So this is a really good indication
that there is something about this color that makes people more attractive.
We also looked at other cultures
and found that in Asian and African cultures the same holds:
people who had a more carotenoid-linked skin color
were seen as more attractive.
And even some people were still arguing back at us and saying,
"Oh, this is just about sun-tanning."
We all like a suntan, so you all know you like to go out in the sun,
you like to go to the beach,
and it leads to of course a somewhat sort of brownish yellowish color on your skin.
This color is caused by a pigment called melanin,
which is activated by UV rays
and it's meant to protect your skin to some degree from a sunburn.
A lot of research in the past has shown
that a suntan is thought of as attractive at least in our societies.
People argued with us, that perhaps,
what is going on is that carotenoid coloration
looks somewhat similar to a suntan; it's also a little bit yellow,
so perhaps people like a tan.
And because they like a tan,
they also like this color which looks somewhat similar.
So we investigated this question.
We investigated it by asking people
which face they prefer
out of a high carotenoid face and a high suntanned face.
So we manipulated the tan in the same way I showed you before for the carotenoids.
And now, let's do this again: who thinks the face on the left is more attractive?
OK, and who thinks the face on the right is more attractive?
Fewer. Interesting.
Right, I'm sure you all now want to know
which of these is the tan and which of these is the carotenoids.
Well, this one if the carotenoid face; and the majority of you prefer this face.
We find the same pattern of results in our research
with eight out of ten people on average
preferring the carotenoid face over a suntan.
That really means that there's something specific
about this color that people like,
even when we compare it to another color
which is normally liked by people in this culture.
This also might actually mean
that the reason or part of the reason we like a tan
is because it mimics to some degree this healthy color of carotenoids.
We've seen that eating fruit and vegetables
makes your skin change color,
and that this new color is seen as attractive.
But remember, at the start, I told you attractiveness isn't the end of the story,
but other traits such as being perceived as more trustworthy or smarter
are also associated with attractive faces.
So we were interested to assess whether these traits
might also be associated with a carotenoid skin color.
We've conducted two studies to date:
we once looked at trustworthiness judgments,
and we also looked at leadership judgments,
so how good a leader people thought a person was.
And in both cases, we found that having a high carotenoid coloration in your skin
influenced these judgments quite dramatically.
People really thought the people with the healthy carotenoid coloration
were more trustworthy and would be much better leaders.
So that should give you some food for thought hopefully.
But to finish off,
there is one important question to answer, isn't there?
How much do you actually need to eat of the stuff?
Do you need to eat 25 carrots every day to get this effect
which might be rather unmanageable?
Well, colleagues at the University of St. Andrews
have conducted a study into this
and found that actually eating only two more portions a day,
this might be for example eating an apple and drinking a glass of orange juice,
or eating a portion of vegetables twice a day,
is enough to change your skin color within six weeks
to be perceived as more attractive.
the difficulty is though, as you might recall,
that if you don't keep it up, your skin color will go back down.
So really what this means is you have to eat
more fruit and veg for the rest of your life.
Thank you very much.
(Applause)