Translator: Hiroko Kawano Reviewer: Peter van de Ven
Wherever you are, you're always using your senses
to give you information about the world around you.
And when you came into the auditorium today,
you've probably looked around, saw the stage setting,
you might have heard the chatter of people excitedly taking their seats,
the quietening hush, and then the voice of the speaker.
But I wonder how many of you
paid attention to the smell of the auditorium.
And actually, we give smell very little attention.
Of all the senses that are giving us information about the world,
it's the one we neglect and we sometimes devalue.
Now that's probably because we think that we only smell when we're sniffing,
that it's only when we're sniffing that we actually get some smell.
But that's not true.
As J. J. Gibson the psychologist said,
we smell because we breathe;
we're actually always being bombarded with lots of volatile molecules.
And olfaction is always on, the processing is always going on.
So the question is, "Why are we not more aware of it?"
Well, lots of people devalue the sense of smell,
including rather famous philosophers.
And it's a famous party game that people play.
If I had to lose one of my senses, which would I willingly give up first?
And it's often smell.
So here's Immanuel Kant saying just that:
"Which organic sense is the most ungrateful
and also seems the most dispensable?
The sense of smell.
It does not pay to cultivate it or to refine it at all
in order to enjoy;
for there are more disgusting objects than pleasant ones
(especially in crowded places)" -
like this!
He says, "Even when we come across something fragrant,
the pleasure coming from the sense of smell
is fleeting and transient."
Now, that's why I think a lot of people believe
that smell could be easily dispensed with.
And a recent survey showed
that many teenagers would rather lose their sense of smell
than give up one of their social media accounts.
(Laughter)
That's how little we care about our sense of smell.
But that's a mistake.
It's a sense that we only recognize the value of
when we lose it.
And when people lose their sense of smell -
often because of head injury, a virus, taking medication,
respiratory infections -
the sudden loss of a sense of smell
comes with a change in their emotional world.
People feel the slight savor to life.
They often develop depression,
and in fact, people who lose their sense of smell
are often depressed longer than those who lose their sight.
It means that we no longer take for granted
the familiar people and places around us.
And it's often smell that's giving us that sense of familiarity.
This is wonderful work
done by these two sensory scientists in Dresden,
Thomas Hummel and Illona Croy,
who've studied the effects on our quality of life,
and there's a huge reduction in quality of life
when we lose our sense of smell.
And as we get older, we'll all start to lose our sense of smell.
Just like eyesight and hearing, it will diminish.
The good news is that right now you can improve your sense of smell,
and I'll tell you a little bit about that later.
But that way in which smell is part of the environment
and makes us feel that we're somewhere familiar,
again, we don't notice it until it's maybe going to be lost.
And the problem here is that smell is very emotionally loaded,
it's very emotionally loaded.
Smell memories, odor memories,
key into some of our oldest and our most emotional memories:
the smell of your grandmother's kitchen,
the smell of a place where you were on holiday.
And some of those things come back
when you just get the briefest whiff of the odor again.
And the olfactory cortex, here,
projects directly to centers of emotional memory,
the amygdala and the inter-rhinal cortex.
Unlike the other senses, it's not gated by the thalamus -
it doesn't go round the brain before it gets to the emotional centers;
it's very direct -
and that's why we get a big charge, emotional charge.
And when people lose their sense of smell, their emotions are depressed;
their emotions are not getting fed with those regular signals.
Here's a gallery I know very well,
and I want to invite you to think about museums and galleries
that you like to visit.
They will have a characteristic smell.
You probably - if you think about it - know how they smell.
This is Kelvingrove Art Gallery and Museum in Glasgow, my hometown,
and it recently went through a major multi-million-pound refit.
And when it was going to be closed for four years to be refitted,
the Glaswegian said, almost as one, "Don't change the smell.
Don't change the smell."
Why?
Because they had been there as children, taken there by schools,
they had gone back as adults and recognized it,
and perhaps taking their own children in turn.
And it always had that familiar smell that they knew so well,
something between stone and furniture polish,
that was very distinctive and characteristic of this place,
and people didn't want to lose it.
And people often think that their sense of smell is probably not so important
because, unlike other animals, maybe we're not good at smelling.
Dogs are very good at smelling; rats are good at smelling;
but maybe we humans are not.
But it's not that we are poor at smelling -
in fact, we've got a superb sense of smell -
we just don't trust our nose.
And we don't use it because we're not on all fours.
The fact that we're standing on two legs and we're looking and hearing,
we use those to detect the environment.
But nothing stops us from being able to be like a dog,
and this is wonderful work by Noam Sobel and colleagues
when he was in Berkeley,
where he got his undergraduates to put on blindfolds
and to follow an odor trail that was chocolate odor.
And the chocolate oder was laid out on the grass,
and it turns out that humans can get to the source of the chocolate.
They are little slower than dogs, they are not as direct,
but they can do it.
So we're underutilizing our sense of smell;
it's there, and it can be used.
Again, our sense of smell is important for signals
that are social signals we give off to one another.
Our body odors actually convey information,
and we give chemo-signals that can affect our own emotions.
Again, lovely work by the Sobel group from the Weizzman Institute shows
that there are chemical signals in emotional tears
that reduce men's testosterone and affect their libido.
Who knew?
Similarly, we can smell fear from other people.
Lovely work by Bettina Pause and Denise Chen
showing that we can smell and be affected by
the body odor of someone who's undergone fear.
And how they do that
is they take T-shirts of people who've been skydiving,
and then T-shirts of people who've been doing vigorous exercise,
and it's the skydiving T-shirts, their smell of fear,
that we can recognize as the fearful ones and also can affect us.
So we're probably chemo-signaling to one another.
Right now, your near neighbors are giving off scent.
And, of course, scent occupies the space between us.
It's there for the taking, but we often don't pay attention to it.
We use it to recognize our nearest and dearest.
Just by their clothes, by T-shirts,
you can recognize whether this is a relative of yours or not.
I know you may have some relatives in mind and think,
I'd know him or her anywhere,
but in general, we can do this,
in general, we can tell, Is this person related to me?
And not only that,
smell is also involved in sexual selection.
So it turns out that you're more attracted to people
whose body odor indicates
that their immune system is further away from yours,
and that if their scent and their body odor
signals that they are too close to you,
you wouldn't find them so attractive.
Somebody's major histocompatibility complex,
in humans called the Human Leukocyte Antigens,
are actually partly responsible for how they smell.
So your smell is due to three things:
It is due to your immune system,
what you eat,
and the bacteria on you.
So when we smell people,
we can, as it were, be sensitive to their attractiveness
because of the distance their immune system is from ours,
and that's going to help the chance of successful reproduction.
So it's very interesting that somebody may be very attractive, very nice,
you might've known them for a long time and think,
"Oh, there'll be a lovely companion."
But if they don't smell right, there's nothing you can do.
(Laughter)
And equally, you can sometimes find a stranger,
and you just suddenly think, "Wow, they're really attractive.
And I was just," you know, "so attracted to that person."
It might be love at first smell,
not love at first sight.
(Laughter)
So, don't neglect it.
But are all the things I'm talking to you about
things that go on unconsciously?
Are these ways of which olfactory processing happens,
but it's not in consciousness?
And might it be that it is only every now and then,
and occasionally things breakthrough into consciousness that smells reach us.
And that might happen because smells are a little overpowering.
It might be that they're a little disgusting.
But it's not just disgusting odors that capture our attention;
it can also be intoxicating odors:
"Wow, that smells incredible,"
"This smells delicious."
And of course, we can direct our attention to bring smell into consciousness
when we pay this sort of attention to people.
And we all go in for sniffing at times
whether it's just to find out whether the milk in the fridge is fresh,
and whether we should continue putting it in our tea or coffee.
Now, of course, as I said earlier,
smell can be trained unlike your eyesight and hearing -
you can actually improve your sense of smell -
and that's what leads to perfumers and wine tasters and coffee tasters
being better than the rest of us.
And in fact, there are changes in the brain:
Perfumers have more gray matter in the entorhinal cortex,
and sommeliers have more dense gray matter in their orbital frontal cortex.
So there is really development you can do that will make a difference,
a real difference to the kind of information
you can extract and what you know.
But, of course, we might wonder,
How good is our sense of smell?
Are there individual differences that matter?
Well yes, there are,
and on average, women are better in their sense of smell than men,
on average,
which doesn't mean there won't be men with a very good sense of smell
and women with a poor sense of smell.
But how do we know what people's sense of smell is?
Well, we can test it.
We can use these sniffing sticks,
a really good test devised by Thomas Hummel's group in Dresden,
where these are pens that you smell -
and some of them are not as good as other pens
we might enjoy on occasion as teachers -
but these allow us to detect somebody's threshold:
When is there a difference between no odor and an odor being noticeable?
Discrimination: Are two odors the same or different?
And finally, identification: Is that rose or mint or leather or tar
when you smell one of these pens.
And the funny thing is
that lots of people who take this test will say to you,
"Oh, I'm no good at smelling;
I really can't do this."
And in fact, they're very, very accurate;
they got a very high score.
And in the contrary sense,
there are people who continuously complain about their awareness of odors,
"Oh, I'm very bothered by smells.
I can smell smells, and I'm perturbed by them.
I've got a very good sense of smell."
But when we test them, they don't have a good sense of smell.
They're either average or poor.
So our awareness of how good our sense of smell is
doesn't correlate with how accurate we are.
That might be a reason why we neglect smell.
But a place where we don't neglect it
and where odor really makes a difference to our experience consciously
is in eating.
But here, smell doesn't get the recognition;
it's due, most of what we call tasting, is due to smell.
So when you think of what the tongue can provide:
it can provide salt, sweet, sour, bitter, umami - savory.
That's about it.
And yet you can taste strawberry, mango, mint, melon, peach -
you don't have peach receptors on your tongue.
That's all coming from smell.
So people who lose their sense of smell will often go to a doctor and say,
"I can't taste anything."
And a good medic will put some salt on their tongue or lemon juice or sugar
and say, "Can you taste that?"
And they'll say, "Yes, but that's all I can taste."
And now they realize how much of tasting was due to smell.
But we confuse taste and smell a lot.
If I give you vanilla pods to smell,
you would say, "Uhm, it smells sweet."
But sweet's a taste, not a smell.
And if I clipped a little bit of the vanilla pod off and got you to chew it,
there's no sweetness in there at all.
It's quite bitter.
So what's happening?
What's happening is that the brain is going from it's usual association
of combining vanilla aroma with things that have sucrose or sugar -
chocolate, ice cream, custard, biscuits -
and it's saying, whenever I get that aroma,
it's usually accompanied by something sweet,
and you transfer that quality of sweetness onto a smell
even though it's not really there.
So we have confusions.
But smell is playing a huge part in food and not getting a look-in.
But it's not smell as we usually think of it,
it's not inhaling molecules from outside;
it's the second source of smell, which is going from the mouth to nose,
up the back of the nasopharynx.
And it's when you swallow or chew food that you pulse odors up to the nose,
and that's when you get a big flavor hit.
So smell, along with touch and taste and temperature,
are all integrated into a single experience of flavor
that we often call "taste,"
and our mistake is,
not crediting smell for playing the largest part in that experience.
But smell doesn't just combine with taste and touch,
it combines with other senses too.
Did you know there are odors in shampoo that make your hair feel softer?
This is strange.
So smell interacts with touch, interacts with taste.
Now our sense of smell, so keen when we're younger,
will start to diminish as we get older.
By the age of 70,
about a quarter of the population are functionally anosmic,
that means they don't have a sense of smell.
And their quality of life will suffer.
They'll be more subject to depression.
They won't take pleasure in their food.
They won't recognize the familiarity of people and places around them.
But we can do something about that.
Because we know from recent research
that smell training, olfactory training, sniffing odors -
if get four essential oils, and you smell them
first thing in the morning and last thing at night,
that will preserve your sense of smell longer as you age,
and it will also make you cognitively more alert.
So it turns out that smelling odors,
smell training,
is better for you than Sudoku.
Do that,
and you'll have a much more active life.
Now people who've never had a sense of smell
often wonder what they're missing.
And they often say, "Well, if I go into -
If we're born without a sense of smell, what is it I'm missing?
What's this invisible thing you talk about?"
And the Spanish philosopher [inaudible] said,
"Maybe it's when I'm in a garden,
and I can see the beauty of the physical arrangement,
but I don't get the odors and aromas, so I don't feel as immersed."
So maybe you feel immersed in a space when you're getting smells.
I notice that we don't notice smell
because we stop paying attention to it when it's familiar.
We no longer notice the smell of our own home.
Everybody else's homes got a smell.
Isn't that odd?
But yours, no.
Well, it's that you've stopped paying attention to it.
But, of course, it's good enough
that if you go home, you'll say something's changed.
"Did I leave the garbage out?"
"Has somebody been smoking?"
So you would notice.
So I think olfaction is not absent,
it doesn't get switched off in the gaps;
instead, olfaction is a constant background to our experience.
Because it's always there, we pay less attention to it,
but it modulates our moods, it affects our attention and awareness,
and it's consolidating our memory of familiar things.
So, many people named here
have helped me in understanding the importance of olfaction.
And all of them would want me to tell all of you
that if you think
you can live just as well without your sense of smell,
you need to think again.
Thank you.
(Applause)