Why can smells unlock forgotten memories?
The toy cupboard at my grandmother's house had a particular smell. I cannot tell you what it was, but sometimes now, as an adult, I will catch a whiff of it. The smell brings with it memories I thought were lost, memories of visits to my grandparents' house, of my grandmother, and of playing with the toys from the toy cupboard. But why do smells have this power to unlock forgotten memories?
Neuroscience is a lot like a detective story – we have to look for clues to reveal the cause. But before we examine the clues, what background information do we have about the case?
What we know is that smell is the oldest sense, having its origins in the rudimentary senses for chemicals in air and water – senses that even bacteria have. Before sight or hearing, before even touch, creatures evolved to respond to chemicals around them.
Sight relies on four kinds of light sensors in the human eye, cells known as receptors, which convert light into the electrochemical language of our brain, and touch relies on different receptor types for pressure (at least four of these), for heat, for cold and for pain, but this pales into comparison for what is required for detecting smell. There are at least 1,000 different smell receptor types, which regenerate throughout your lifetime, and change according to what you are used to smelling. The result of this complexity is that we are able discriminate many, many different kinds of smells.
We do not, however, have names for all the smells we can differentiate. Smell is perhaps the sense we are least used to talking about. We are good at describing how things look, or telling how things sounded, but with smells we are reduced to labelling them according to things they are associated with ("smells like summer meadows" or "smells like wet dog", for instance). An example of this “hard-to-talk-about-ness” is that while we have names for colours which mean nothing but the colour, such as “red”, we generally only have names for smells which mean the thing that produces that smell, such as “cedar”, “coconut” or “fresh bread”. [continue]
Smell (and associated taste) is our most ancestral sense, and it is much more powerful than we usually give it credit because it flies under the radar; it mostly speaks to our unconscious. Jonah Lehrer made a good point of this in his book "Proust was a neuroscientist".
Nice article. I like the stuff about we don't really have names for the smell themselves, but rather for the things that produce them, or what it smells like. Smell is very, very good at evoking emotions, including sexual arousal. Smells are so powerful, they can often change our moods without us being very conscious about it. The smell of the sea, in particular the smell of the Atlantic Ocean, for example, never fails to lift my spirits, whether in summer or in winter. It smells like my childhood.
I like the stuff about we don't really have names for the smell themselves, but rather for the things that produce them, or what it smells like.
I thought that was very interesting, too. I'd never thought of it that way. Perhaps we consider smell to be a more innate property of something than say its size, color, or texture. I mean, apples come if different sizes and colors, but they all smell like apples.
I totally agree with your last few sentences.
I do agree that smells or "an odor" can bring back memories or bring about a state of mind, a state of well-being (what does incense exists for ?) or a state of sexual arousal (all hose pheromerones hanging about ?). Some smell are really associated to some memories I have, though I could never describe them in words, like the smell of the farm my parents used to take us for summer). I like the smell of spring, of fresh flowers ( like almost everybody) and dislike some smells of body odors ? are we too amercan ?)anyway, I believe smells is a whole world to discover and I think animals and insects have already understood that...!
I think we all dislike certain body odors. But others are appealing, like the smell of the people we love, the smell of babies and little children, etc. But I'm talking about subtle smells, not rancid sweat, etc.
Who doesn't love the smell of baby, especially with roasted potatoes and carrots? Oh, sorry, my inner atheist was showing there.
Yeah, I like manly smells myself. Not rancid, as you say, but au natural. That's a big turn on. And those familiar bodily smells can be comforting. There's this wonderful scence in Love is the Devil in which after his lover's suicide, Francis Bacon (played by Derek Jacobi) still mourning, picks up his pillow off the bed and breathes in the smell of it.
Wow, that's Daniel Craig! I haven't seen this movie, looks good!
Ah, OK. Thanks.