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Don't you wish you could smell as well as a dog?
出典: Philip Ball, writing for the Observerm May 14, 2017
https://www.theguardian.com/science/2017/may/14/dont-be-sniffy-if-you-smell-like-a-dog
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Don’t be sniffy if you smell like a dog
New research debunks the belief that humans’ sense of smell compares poorly with that of our canine friends
Philip Ball
Philip Ball
Sun 14 May 2017 06.59 BST Last modified on Wed 21 Mar 2018 23.52 GMT
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Dogs can follow scent trails – but so can humans.
Dogs can follow scent trails – but so can humans. Photograph: Alamy
Don’t you wish you could smell as well as a dog? Actually, you probably can. In a paper published in the new issue of Science, neuroscientist John McGann of Rutgers University in New Jersey describes the idea that humans have a poor sense of smell as a “19th-century myth”. On the contrary, he writes, “humans have excellent olfactory abilities”. So why have we been doing our noses down?
We’ve never had a high opinion of smell. Ever since Plato pronounced it inferior to the “noble” senses of sight and hearing, there’s been a lingering suspicion that there’s something primitive and animal about it. For Charles Darwin, our atrophied sense of smell was a mark of evolutionary advancement beyond our ape ancestors.
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An upright posture also meant that we were no longer on a level with one another’s smelly parts. An excessive interest in the anal and genital was, for Sigmund Freud, a sign of arrested development, possibly perversion. With the repression of smell, he said, came repression of uncontrolled sexual impulses and the emergence of civilised behaviour; taking too much pleasure in smell was suspect. Freud noted that only infants didn’t seem repelled by the smell of faeces.
“Freud believed that smell was part of a tension between our animalistic roots and our rational higher nature, which could be a source of neuroticism and mental disorder,” says McGann.
But a scientific disregard of our sense of smell didn’t start with Freud or Darwin, McGann says. He puts much of the blame on the 19th-century French physician Paul Broca, an expert on the anatomy of the brain. Broca is mostly remembered now for having identified a region of the brain’s frontal lobe associated with language processing, which is named after him. He believed that this region was the source of the “enlightened intelligence” of humans and that its development crowded out the part of the brain that processes smell: the olfactory bulb. In humans, the olfactory bulb is relatively small compared with rodents and most other mammals and is tucked away rather than sticking out at the front of the brain.
“Broca viewed smell as an animalistic sense that drove irrational behaviour and thus must be diminished in importance in a rational being with free will,” says McGann. He has traced the evolution of that view into a prevailing medical opinion that humans have a poor sense of smell.
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Case closed: sniffer dogs provide a service few people would consider for a career. Photograph: Steve Parsons/PA
But smell scientist and psychologist Avery Gilbert thinks that Broca wasn’t so far from the truth in some ways. The repositioning of the human olfactory bulb beneath the frontal lobe, he says, enables us to integrate smell into our other mental processes: not just to sense it and respond automatically, but to think about it. “It lets us freely assign different emotional values and meanings to a given odour, indeed to treat a smell as a symbol,” he says.
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Besides, a relatively smaller olfactory bulb doesn’t mean we’re poor smellers. As McGann shows, the absolute size of the olfactory bulb – the total number of neurons it contains – is about the same in all mammals, from mice to men. What’s more, sensitivity to smell depends on the odourant: we’re much better than rats or monkeys at detecting one of the odourants in freshly brewed coffee, for example.
To experts in the science of smell, it’s not news that we’re better smellers than popular belief allows. “There’s a long history of olfactory specialists arguing that human smell is actually quite good,” McGann says. “But somehow the myth has persisted anyway, both in the general public and in broader scientific world.”
Dogs have some advantages. “They have nostrils and scent-sampling behaviours that are more efficient than ours and they devote more of their brain and behaviour to investigating and analysing smells than we do,” says Gilbert. But we’ve also bred them partly for olfactory prowess, especially at a distance. “They’ll always smell an elk a hundred yards off before we do.”
The sensitivity of a trained tracker dog might be hard for humans to match. “Dogs who can follow the smell of a person through field and forest after having smelled a scarf have a sensitivity we can only dream of,” says smell expert Luca Turin, author of Perfumes: The A-Z Guide.
Yet on the whole humans compare pretty well, especially for close-up smells, where dogs tend to rub their noses on the source rather than relying on airborne scents. “Human smell is not the same and dogs or rodents, but it’s clearly not notably worse,” says McGann. “If you restrict testing to traditional, volatile odours, then dogs and humans stack up pretty well against each other.”
Similarly, we use sniffer dogs not so much because they are extraordinary smellers but because they can be highly trained. For example, they are currently being used to sniff out molecules produced by cancer cells in human clinical samples. But we could probably do such things too, says McGann. “Humans can follow scent trails through a park and medical technologists have been smelling urine samples for diabetes for decades.”
As for drug detection, “we can probably detect cocaine at levels comparable to dogs”, Gilbert says, “but few of us are willing to make a career of crawling around airport luggage carousels to find the stuff”.
Our belief in our poor sense of smell might be partly self-perpetuating. Discouraged by the myth, and subliminally worried by the Freudian message that enjoying smell is infantile and perverse, we don’t develop the habit – or the vocabulary. “Sommeliers and perfumers do have very developed senses of smell,” says McGann, “but this often comes about through practice and training on how to label smells that most lay people don’t know the words for.”
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So now you can relax and release your olfactory skills. “I can tell you from personal experience,” says McGann, “that if you put your nose on the ground and smell, you can find a fascinating world of stimuli you never noticed.”
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It turns out, Hollywood got it half right.
出典: Panos Athanasopoulos, writing for the Conversation, June 13, 2017
http://theconversation.com/language-alters-our-experience-of-time-76761
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Language alters our experience of time
June 13, 2017 10.53pm AEST
Amy Adams in Arrival. Paramount Pictures
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Panos Athanasopoulos
Professor of Linguistics and English Language, Lancaster University
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It turns out, Hollywood got it half right. In the film Arrival, Amy Adams plays linguist Louise Banks who is trying to decipher an alien language. She discovers the way the aliens talk about time gives them the power to see into the future – so as Banks learns their language, she also begins to see through time. As one character in the movie says: “Learning a foreign language rewires your brain.”
My new study – which I worked on with linguist Emanuel Bylund – shows that bilinguals do indeed think about time differently, depending on the language context in which they are estimating the duration of events. But unlike Hollywood, bilinguals sadly can’t see into the future. However, this study does show that learning a new way to talk about time really does rewire the brain. Our findings are the first psycho-physical evidence of cognitive flexibility in bilinguals.
We have known for some time that bilinguals go back and forth between their languages rapidly and often unconsciously – a phenomenon called code-switching. But different languages also embody different worldviews and different ways of organising the world around us. The way that bilinguals handle these different ways of thinking has long been a mystery to language researchers.
Time, imagination and language
Time is a case in point. Time is fascinating because it is very abstract. We cannot touch or see it but we organise our whole lives around it. The really cool thing about time is the way we actually experience it is in some ways up to our imagination and our language. Because time is so abstract, the only way to talk about it is by using the terminology from another, more concrete domain of experience, namely that of space. For example, in Swedish, the word for future is framtid which literally means “front time”. Visualising the future as in front of us (and the past as behind us) is also very common in English. We look forward to the good times ahead and to leaving the past behind us.
But for speakers of Aymara (spoken in Peru), looking ahead means looking at the past. The word for future (qhipuru) means “behind time” – so the spatial axis is reversed: the future is behind, the past is ahead. The logic in Aymara appears to be this: we can’t look into the future just like we can’t see behind us. The past is already known to us, we can see it just like anything else that appears in our field of vision, in front of us.
Amy Adams as linguistics expert Louise Banks in Arrival. Paramount Pictures
These differences in how time is visualised in the mind affect how Aymara speakers gesture about events. Those that are bilingual in Spanish (a future-in-front language like English) tend to make forward moving gestures, whereas those with little or no knowledge of Spanish gesture backwards (consistent with the Aymara future-is-behind pattern), when talking about the future. Mandarin Chinese employs a vertical time axis alongside a horizontal one. The word xià (down) is used to talk about future events, so when referring to “next week” a Mandarin Chinese speaker would literally say “down week”. The word shàng (up) is used to talk about the past – so “last week” becomes “up one week”. This affects the way observers perceive the spatial unfolding of the ageing process.
In one study, Chinese-English bilinguals were asked to arrange pictures of a young, mature, and old Brad Pitt and Jet Li. They arranged the former horizontally, with the young Brad Pitt to the left and the old Brad Pitt to the right. But the same people arranged the pictures of Jet Li vertically, with young Jet Li appearing at the top and old Jet Li appearing at the bottom. It seems that culture and meaning form a tight bond as this context-dependent shift in behaviour shows.
Our study showed that these language differences have psycho-physical effects in the bilingual mind: they alter the way the same individual experiences the passage of time depending on the language context they are operating in. For example, Swedish and English speakers prefer to mark the duration of events by referring to physical distances – a short break, a long party. But Greek and Spanish speakers tend to mark time by referring to physical quantities – a small break, a big party. Speakers of English and Swedish see time as a horizontal line, as distance travelled. But Spanish and Greek speakers see it as quantity, as volume taking up space.
As a consequence, English and Swedish monolinguals estimate how much time it takes for lines to lengthen across a computer screen based on how far the lines expand. If two lines stretch to different lengths over the same time period, participants judge the shorter line to have travelled for less time than it actually did and the longer line to have travelled for more time than it actually did. Spanish and Greek monolinguals on the other hand are affected in their time estimations by physical quantity – how much a container has filled with liquid. If two containers fill up to different levels over the same time period, participants judge the container with the smaller amount to have filled in less time than it actually did and vice versa.
Flexible bilinguals
But Spanish-Swedish bilinguals are flexible. When prompted with the Swedish word for duration (tid), they estimated time using line length. They were unaffected by container volume. When prompted with the Spanish word for duration (duración), they estimated time based on container volume. They were unaffected by line length. It seems that by learning a new language, you suddenly become attuned to perceptual dimensions that you weren’t aware of before.
The fact that bilinguals go between these different ways of estimating time effortlessly and unconsciously fits in with a growing body of evidence demonstrating the ease with which language can creep into our most basic senses, including our emotions, our visual perception and now it turns out, our sense of time.
But it also shows that bilinguals are more flexible thinkers and there is evidence to suggest that mentally going back and forth between different languages on a daily basis confers advantages on the ability to learn and multi-task, and even long term benefits for mental well-being.
So, to refer back (or is it forward?) to Arrival. It’s never too late to learn a second language. You will not see into the future, but you’ll definitely see things differently.
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