Smells like… something

Why is smell the oft forgotten sense, and where does following our nose take us?

Things mentioned in this podcast

• Wired article on why smells are hard to describe
• Smell and the reminiscence bump

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Hello and welcome to the Cognitive Engineering Podcast produced by me, Fraser McGruer, for Aleph Insights. In this series of podcasts, we take a look at interesting topics and discuss what we think they tell us about analysis and decision making. I'm here with Chris Wragg, Peter Coghill and Nick Hare of Aleph Insights. And this week we're discussing appropriate smells and inappropriate smells. Chris, kick us off. Why? Yeah, what?

Yeah, well, so I was regaling the team with an anecdote that is far too offensive to be broadcast here. But essentially, the sort of story boiled down to, you know, why it is OK, for example, for parmesan to smell of parmesan, but not, for example, someone's feet. You know, why some smells are OK associated with some things, but not with other things. And so, you know, that got us sort of talking quite a bit. But then also just more generally, you know, what is going on with smell? You know, it's an interesting sense and one which is... It's the bad boy of the sense family. It's the bad boy of the sense family. Yeah. So we thought it would be interesting to discuss kind of, you know, smell context and appropriateness, but also just more generally.

OK. I mean, it's more visceral than all the other senses. We don't get repelled by stuff in the same way or, you know, or. Well, anyway, smells, as far as I'm concerned, it's information processing, so it belongs in the podcast. It's allowed. OK, so well, let's dive into some other. Unfortunately, it's a shame because we cannot use, as you say, the example you mentioned was a great example. Can't use it. So look, we talked about parmesan and feet. What other examples can we think of? Garlic and breath. I love the smell of garlic, but not when it's coming out of someone's face. Yeah, I've pretty much never experienced that sort of repellence to repulsion of someone's breath smelling of garlic. Maybe it's because mine always smells of garlic. I've never smelt any. Except for once when I got walked. I just arrived in Switzerland at Geneva Airport. I jumped into a taxi and the whole taxi reeked of garlic. Right. The bloke must have just come across the French border. But you weren't you weren't tempted to scoff some delicious, you know, food. But that's about the only time I remember going, oh, my God, this place thinks of armpits and curry. I mean, I love the smell of curry when it's curry, but not if it's my own armpit. OK, but have you ever smelt curry that smell? Yeah, my own armpits. Yeah. After I've eaten curry. Oh, OK. So you so you don't make curry. Obviously, what with them being my own armpits, I don't really mind. I'll happily give them a sniff, you know, but to remind you of yourself, the delicious meal. Yeah, exactly. If it was someone else's armpit that was being forced

to sniff, it wouldn't be pleasant at all. Yeah, I I worked with somebody once and they smelt of shaken vac. The the yes, the product for cleaning, cleaning carpets doesn't sound too bad. The freshness. No, no. But, you know, it was OK on carpets, but but less so. Had they mistakenly

used it as an underarm deodorant? Well, I don't know. Yeah. Maybe the reason is talcum powder.

I think you've described half the civil service there. Peter, any any examples? Well, well, sweatiness is OK on the football pitch or in the gym, but you wouldn't want your colleague to not have a shower when they come back to the office. Yeah. Yeah. Isn't that more about, though, that

it's outdoors when they're when they're running? And I'm not sure I'm not sure sweatiness. I mean, sweatiness itself is OK, but the smell of stale sweat. It's the stale sweat. It's really. Yeah.

It's really pleasant. And I mean, there's a famous saying, well, I hope it's famous, which is every man. Get out phrase, you stink. Everyone's always saying that. Yeah. The famous phrase, every man loves the smell of his own farts. Yeah, I've heard that as much as they like the look of their own handwriting or something. Yeah. Yeah. Well, my handwriting is pretty awful. My farts are fine. But no, but there is that there is some truth in that. Other people's are like, oh, my God, that's terrible. One's own pungent and to be, you know, relished. Yes. No, I don't. Well, not really.

I mean, presumably, you know, there's a reason for that, which is that you have to. You've got to live with yourself. You've got to live with yourself. Exactly. Whereas, you know, other people less, less so. And you would probably. Well, it's a bit like tickling yourself as well. I mean,

it's just somehow, you know, you know, it's just been inside you. Right. So how bad can it be? It's just you're just recycling it. Okay. So where do we go with this? Sorry. We've

already just started. I'm not sure where to go. So smells. Well, I was going to. I mean, I think it's quite interesting just looking at what is going on when you're smelling. Nick was talking about being, you know, information processing. So maybe just thinking actually what's happening, you know, and the fact that an odorant is a, you know, a physiochemical molecule binding to a specific receptor. You know, those receptors are located in the olfactory epithelium in the up in the nasal cavity. And they send messages to the olfactory bulb where, you know. It's pretty complicated, actually. Pretty, pretty complicated. But also then what's really interesting, I think, why smell is so interesting is the interaction with other parts of the brain, like the hippocampus and the amygdala and why you smell has, like you were saying, more visceral, right? Why it's more attached to emotions and so on. So I think all of that's quite,

quite interesting. But I think it's physically and neurologically close to the memory center of the brains, the amygdala and the hippocampus are crucial in memory recall and memory formation. And hence why there's an intuitive, intuitiveness about why it's so visceral and so emotive when you smell, more so perhaps than visual stimuli.

Or audio or similar. Yeah. Okay, well, I mean, that's what it is. That's what the process is. And that's why it's so emotive. What's next?

Well, so I think the link between smell and it's sort of, it's very associative. And I think that's interesting, right? So there are all sorts of things, as we're saying, it's important to memory. So the phrase like redolent, you know, is about a smell that is reminiscent of something, and this has always been intuitively known, but now we understand a bit more about it. But, you know, it's in humans, it's important for things like maternal bonding, and like recognition of. And paternal bonding as well. Well, and paternal bonding, but particularly the smell of breast milk and that, you know, when before a baby can see its mother, it can recognize the smell of

its mother and so on. So basically smell is going away, doing all this stuff under the surface

that we're barely aware of. And it's the under the surface bit of it that's really interesting.

Because apparently it also, yeah, we can smell, we can recognize our own family from smell. Subconsciously, we don't think we can, but we can. There's some theory that that's to do with incest avoidance as well. So this starts to, so this kind of emotional connection starts to perhaps answer our question, why is it okay for parmesan to smell like parmesan, but not feet Sort of. I mean, although it presents a bit of a puzzle, which is that we think of smells as being processed in a very subconscious automatic reptilian type way, but obviously actually we can still impose our emotional reaction is still going to be conditioned by other things that we happen to know. So for example, I mean, honey, people think they like the smell of honey, but when they're asked to just smell honey, a lot of people report finding it repulsive. So, you know, that is clearly the niceness of the smell of honey is conditioned by something we know, which is that

it's honey. And I think, you know, there's this really interesting distinction between sort of explicit odour memory and implicit odour memory, and that we're not particularly good at the explicit odour memory. So things like smell recognition, like, you know, sort of specifically being asked to identify an odour. So, you know, what does this thing smell of? We're not so good at, but the implicit odour memory where you are, you know, there are these like weird kinds of experiments they run where you get people in a set of rooms and you pervade the room with particular smells. And then you ask them a series of questions about the appropriateness of smell to particular pictures of rooms and so on. And they're able to associate smells with particular rooms really well, even though if you say, when was the last time you smelt this particular smell? You know, it might be a smell of leather or something. People go, oh, you know, I don't know. And it was, you know, it was a smell that was used in this experiment. They, when asked which of these smells goes well with this room, they sort of generate that association again. So it was, you know, as Nick was saying, this kind of what's going on under the surface and our attachment to things which we, it seems like we're not particularly aware of smells as they're happening, or we're not particularly aware of the building up of the memories of those smells. But the things we do recognize like visual cues and that we are good at saying, oh yeah, the last time I saw that thing was so-and-so, they get attached to the smells. And so you get this

sort of. Okay. Yeah, there's a question about describing smells. Sorry, I want to hear more

from Peter. Okay. Yeah, I think picking up what Chris is sort of suggesting, I think there's good, there's some neurological reasons for it. Like we mentioned that the smell stimulates parts of the brain closer to the memory formation, et cetera, which might make them more emotive and associative with memory. And I think, but also the, conversely, the visual and auditory parts of the brain are closer to the language centers of the brain. So I think what's happened in evolution of our species is that as we started moving around the world and finding out more about it and how to sort of solve problems in it, the visual and auditory parts became more important for the interaction parts and the sort of social parts as we developed. And the smell bits and the taste bits got kind of not relegated per se, but kind of weren't as developed as much as the audio. Anecdote, I mean, sort of thinking about this and how my own perception of the world kind of works, I haven't got a very well-developed vocabulary to describe features of smells as much as I have visual or audio. So visual, you use words like round and straight, and you can fairly accurately and concisely describe what you're seeing to somebody else. I haven't got nearly that depth of vernacular to describe a smell to someone over the phone. Well, that's,

that's, but that's not, you're not alone. That's nearly universal. And I, so, I mean, on one hand, yeah, you're right that we, we have trade, primates particularly have traded away smell in favour of vision. So primates and apparently also whales and dolphins, they can't be, they're not fussed about smelling things either. But we, we basically don't, you know, we obviously have much less well-developed sense of smell than, for example, your dog or cat. But I think there's also, I mean, it's, if you think about the intrinsic, the type, the way that smell works, as Chris was saying, the way that your olfactory epithelium works is it isn't based on the, the isolation of sort of abstract features of smells. It is basically a big bank of smells that are either triggered or not, you know, hundreds, several, several hundred, 400 or something different types of receptor, which in different combinations will produce different smells. But they're not on a continuum, right? So whereas you can describe, for example, you know, vision in terms of a continuum, you can say there is an area of vision here, or you can describe a shape, you know, in abstract terms, or a colour in abstract terms and colours come on a continuum. And so you can say this is more or less red. You can't do that with smells. You can't say this is more or less, you know, of the smell of an egg. It just, it isn't a continuous thing like that. So in a sense, like in order to be able to do that, to describe smells in abstract terms, which is what we need to do to be able to have this vocabulary of smells, so that I'd be able to say, what does this flower smell of? And I'd say, well, it's a little bit, it's sort of slightly grew and, but it's quite shme, and that would tell you what it smells of. Smell would have to work differently. I mean, it just doesn't work like that, you know? So I think we always need hundreds and hundreds of those words, and it's just not

worth the, you know, the while developing them. I think there's two things there. One is the attachment of smells to verbal labels is apparently something that's been picked up. It's difficult. You know, you smell something and go, yeah, what is that? Whereas if someone shows you an orange, you're like, it's an orange, you know? I mean, that's not quite true. You would probably recollect the smell of an orange, but generally that attachment between the sense and reaching for the verbal label for it is apparently quite bad. But then I suppose, you know, there is an element of smell not being that dissimilar to the way we receive visual cues in that, you know, you've got those different rods in the eyes that, you know, pick up the different prime colors and effectively mix them.

There's only three of them. Yeah, there's three of them. See, we can talk about things being red or blue or green, but there's 400 of them effectively in the nose. And that they're mixed, yeah.

I think the smell is not, it's not binary. Each of these senses is not binary. They do indicate strength of signal as well. So you've got potentially a greater information set than your, the cones and rods in your eyes, which detect intensity, but also color in three bands. So it's just, I think it's just that we just don't use it. We don't, we don't, haven't trained our brains to use it either culturally or evolutionarily. But you could, if we needed to, we could, we could sort of regain it a bit. I mean, that's a really interesting

point because, you know, and we probably don't, we probably don't train to use it because it's not as good as our other stuff. So like, if you think about kids, right, one of the things they were suggesting, the reason we're not good at recollecting smells is because we don't have any formal education for it. The first thing you do with a baby, right, is you give them one of those books with, you know, apple, picture of apple, here's an apple. You don't waft things under their nose and say, apple, apple, you know, we don't, but that's because it's not, it's not as useful to us. So we don't invest that in that. Vision is so useful for our communication. Exactly. And the other thing I was, which picks up on Nick's point, I was going to say is that intensity of, of smell. Do you know how they, how they measure sort of smell intensity? Because there's obviously you can't sort of, you know, there's a, there's a physical property to light waves, you know, that you can sort of measure separately from us, but smell is very much about perception. It's a bit of a, bit of a weird thing, but there's something called the olfactory perception threshold, right? And basically what this is, is they release a smell into an environment and they get a group. And at the point at which 50% of the people go, I can smell it now. That's the threshold. And by definition, one odor unit that you, at that point, you have one odor unit per cubic meter of that thing. So you define intensity of smell by people's ability to detect it. Whereas, you know, obviously decibels and, you know, frequencies of light are not detected in relation to our ability to perceive them.

You tend to measure sound intensity in the same way. It's decibels is decibels. That's intensity in a logarithmic unit below the average, below the 50% point at which people would hear it.

I think in principle, you could measure smell in terms of parts per million of certain molecules, but the point is the sensors are really complicated. We don't really need to. I mean, they do a similar thing with Scoville scale, which is how hot chilies are by watering them down until people can't taste them anymore. So, yeah, I mean, that just seems to me like, presumably, I'm not an engineer. That's Peter's job. But presumably we could create sensors for all of these things. But we just there's no point because I think it'd be quite fun to make a

child's book that was a sort of scratch and sniff that educated them more about smells.

But you could I mean, I mean, I've been exposed to the smell of coffee and oranges and stuff my entire life. And I but but at the same time, apparently tests have shown that people are really bad, even at recognizing things like the smell of coffee. It's 50%, you know, but people will be able to name it. So I don't know. I feel like this could be one of those weird experiments where you spend 20 years trying to get a kid to recognize smells. And at the end of it, they're useless. I don't know. Like I mean, that's the question. Are we are we intrinsically bad at it? Which is what some of the but sorry, just in favor of Peter's hypothesis that you can learn it that are the apparently the money can do high speakers of Southeast Asia, okay, the well known money can do high speakers, they they apparently do smell is very important to them. And because of that, you know, being able to smell leaves and being able to smell animals and that kind of thing. I don't know why them more so than anyone else, but it is. And so they've been documented as having they have abstract smell names. So they have for a word that is sort of like means the smell of a badger in the dry season or smelling tasty like cooked food or smelling like something that will attract tigers. Now those aren't those we can't translate the words so that where they've been translated into something which sound like, oh, it's the smell of oranges, but it's not it's an abstract term. That isn't the smell of some specific thing. You know, because we don't have

kind of like aromatic or spice spicy. Yeah.

I smell it, it takes me back to a different time. Yeah. Okay. Peter. The smell of cooking meat, specifically beef, I can go from I will instantly make... Frying? Well, no roast, anything roasting or barbecuing. I'm actually, I'm actually salivating as you're talking. Yeah, it will make me instantly hungry, feeling instantly hungry. Similar to that coffee and chocolate. They have a similar sort of effect. There's a particular smell which I can't pin down, but it's a sort of it's a kind of disinfectant cleaner smell. Yeah. That reminds me strongly of school. It was a particular brand or particular chemical that they used at school that reminds me of a nice sort of innocent, safe time, very young age. And occasionally I pick it up in public buildings and places. They obviously use the same chemical at random. And that's very evocative of particular memories. That's a nice smell. And the other thing, the other smells are quite like a DIY smell. So the smell of sawn wood, the smell of sort of plasterboard, you know, being drilled, stones being cut, metal, and the smell of oil and metal reminds me of working on bikes and the smell of bicycles

and things. Reminds him of the day he was made in a workshop by a kindly carpenter.

So that's quite a pleasing smell. That's a very good, that's an interesting one because you smell quite a lot to smell when some, to help diagnose what problems are because clean, fresh grease smells very different from dirty, contaminated grease. So you can, when you take something apart, just cleaning it up will often solve the problem. And it's the smell that tells you that the grease is often bad. Yeah. Yeah. Okay. Nice, nice collection.

Chris? Well, for me, I think bookshops like, and usually independent bookshops, you know, have a sort of, I don't know, they just have a smell of freshness and knowledge, knowledge. Yeah, it's the smell of knowledge. Yeah. Then I think there's a particular type of, it's maybe a Clementine, or some sort of tangerine that you get at Christmas, which are really, really, like taut and, and lovely. And they're the Christmas ones. And so I associate that with Christmas and, you know, that I, they smell really nice. Yeah. And then I think the third one for me is wallflowers. I love the smell of wallflowers always, always. I don't know what they're like. Yeah, I know. Yeah, they're the sort of shy girls, you mean? Yeah, that's right. Easy to prey on. Yes. No, I mean, the, the, the bloom. Okay. You know, for me, I think my top

one is actually the same as Nick's is smell of in very particular of my, of my daughter's newborn head, her hair, that sort of sweet baby smell. Beautiful. The other one is autumn. I love autumn. It's my favorite season. And that's a rain on leaves. And what I like about autumn as well is the fact that it's that sort of, it's a kind of sweet sorrow thing. It's sort of the year coming to an end, winter is coming. But it's certainly in the UK, it's sort of a start of a new academic year. And so sort of new beginnings. There's something about that I quite like. Make a persuasive case. Yeah. And then the third one is actually very specific, and goes back to one smell at one time, which was about 15 years ago, I broke my arms really badly. And I was in hospital for quite a while after a car accident or Paris. So, so, so what it was, was I was being tended to by all sorts of different nurses. There was this one nurse who was a larger lady, and she just had a very distinctive smell about her. And it was just immediately affecting on me. And I just she imprinted herself on you. Anyway, so those are my favorite ones. Least favorites. Let's make these

ones quick. Peter. I'm still struggling to think of one actually. Chris. So for me, it's manchego cheese. The point at which I liked manchego cheese. And then my wife pointed out to me that it smells of vomit. And I now can't touch manchego cheese. That's a real shame. I love that. That's

a shame. It's funny. I can switch it off when I know it's not vomit. Okay, Peter, the smell of

magnolia flowers. They have a they have a sickly, nasty sort of smell, in my mind anyway, much like in the same way that the the paint color, the emulsion color is just horrid. Okay, yeah, something bodily about some flowers. And you sometimes get magnolia flavored soap, and there's some at my parents house at the moment, and it hasn't been touched. It's the bottles been there for about five years, and no one uses it because it's horrid. Okay, right. What's that flower that

smells of semen? That's not. Yeah, there's there's lots of sometimes you get a tree or a flower, which is, you know, in the street, and it's a really. Yeah, not mad about that one. Nick. Well, it's boring, because it's similar to Chris, but it's my friend Steph's car. It's the worst smell I can remember for for the last decade or two. She's got three travel kit boys who had all travel sick. And it was just so she gave me a lift down to the shops a few couple of months ago. And it was just it was just like having my head in a bag of vomit. I'd say by window. She was completely immune to it. I found it unbearable. I was virtually on the on the on the edge of being sick myself. So Steph's car smells of Mantego. Yeah, exactly. Well, my car's a bit like that. We used to nickname it the vomit comet. Yeah, because one of my kids Yeah, he just probably used to throw up in it. My least favorite smell tequila. Tequila. I just just because every time I've ever drunk it, I vomited. So I smell it and I get the shivers, you know, seems like vomit is a popular one for not being an unpleasant smell. Right up there, isn't it? Yeah, yeah. Okay. Well, on that pleasant note, we will we will draw things to a conclusion there. Thank you, as always, for listening to the Cognitive Engineering podcast. I'm Fraser McGruer. You've been here with Nick Hare, Peter Coghill and Chris Wragg of Aleph Insights. Until next time, goodbye.