一項(xiàng)令人驚訝的新研究表明，你也能夠在草地上跟蹤一種氣味,，但前提是必須要趴在地上,，并且將鼻子貼近地面。這一發(fā)現(xiàn)不太可能讓獵犬和毒品嗅探狗失業(yè),，但它卻能夠?yàn)槿祟?ldquo;可憐的”嗅覺(jué)贏得一點(diǎn)點(diǎn)尊嚴(yán),。
人類普遍認(rèn)為自己并不善于追蹤一種氣味，尤其是在與其他哺乳動(dòng)物,，例如狗和嚙齒動(dòng)物相比時(shí),，這一弱點(diǎn)更是暴露得一覽無(wú)余。但是很少有人對(duì)此真地進(jìn)行試驗(yàn),。由美國(guó)加利福尼亞大學(xué)伯克利分校的Jess Porter和Noam Sobel領(lǐng)導(dǎo)的一個(gè)研究小組,，用巧克力香精浸泡了10米長(zhǎng)的線繩，并將其放置在一片草地上,，從而形成了兩條夾角為135°的直線,。隨后，研究人員為32名大學(xué)生戴上眼罩，并讓他們穿上耳套,、厚手套和護(hù)膝,，目的是防止他們獲得嗅覺(jué)之外的任何感官暗示。當(dāng)這些大學(xué)生完成了在草地上進(jìn)行的測(cè)試后,，2/3的受試者都能夠成功追蹤氣味,，他們就像獵狗跟蹤野雞一樣，來(lái)來(lái)回回地呈“之”字形前進(jìn),。研究人員在12月17日出版的《自然—神經(jīng)科學(xué)》雜志上報(bào)告了這一研究成果,。
Porter表示，幾乎所有的受試者都認(rèn)為這項(xiàng)試驗(yàn)具有挑戰(zhàn)性,，然而其中的4名大學(xué)生通過(guò)實(shí)踐提高了自己的跟蹤技能,。經(jīng)過(guò)幾天的練習(xí)，他們學(xué)會(huì)了如何更快地跟蹤氣味以及減少偏差,。盡管如此,，他們的表現(xiàn)依然不及其他研究人員對(duì)狗進(jìn)行的測(cè)試,。另一項(xiàng)針對(duì)嗅覺(jué)進(jìn)行的實(shí)驗(yàn)表明,，人類能夠利用兩種方法確定氣味——比較連續(xù)呼吸間的氣味強(qiáng)度以及比較一次呼吸中兩個(gè)鼻孔的氣味強(qiáng)度。
耶魯大學(xué)的神經(jīng)學(xué)家Gordon Shepherd表示：“這是一項(xiàng)具有創(chuàng)新性的工作,，它對(duì)人類的實(shí)際嗅覺(jué)能力進(jìn)行了梳理,。”Shepherd說(shuō)，我們?cè)僭O(shè),，在人類的靈長(zhǎng)類祖先開(kāi)始用兩條腿行走后,，他們的嗅覺(jué)功能便逐漸減弱。與其他動(dòng)物將鼻子貼近地面相比,，靈長(zhǎng)類動(dòng)物的嗅覺(jué)受體基因已所剩無(wú)幾,，這似乎支持了上述觀點(diǎn)。然而Shepherd指出,，這項(xiàng)新的研究表明,，“如果能夠重新四肢著地、貼近地面,，我們或許能夠完成一些之前想都不敢想的事情”,。
英文原文：
Human Scent Tracking Nothing to Sniff At
A surprising new study suggests that people can track a scent across a grassy field--at least if they're willing to get down on their hands and knees and put their noses to the ground. The findings are unlikely to put hunting hounds and drug sniffing dogs out of work, but they may earn a little respect for the poorly regarded human sense of smell.
Humans are widely believed to be poor at tracking scents, especially when compared to other mammals such as dogs and rodents. But few had ever put that idea to the test. A research team led by Jess Porter and Noam Sobel at the University of California, Berkeley, dipped 10 meters of twine in chocolate essence and laid it in a field to form two straight lines connected at a 135° angle. Then they blindfolded 32 undergraduate students and had them don earmuffs, thick gloves and kneepads to prevent them from using sensory cues other than smell. When set loose in the field, two-thirds of the subjects successfully followed the scent, zigzagging back and forth across the path like a dog tracking a pheasant, the researchers report online 17 December in Nature Neuroscience.
Nearly all the subjects reported that the task was challenging, Porter says, but four of them got a chance to improve with practice. Over the course of several days, they learned to follow the trail faster and deviate less. Even so, their performance remained well below what other researchers have reported in dogs. Additional experiments with noseplugs suggested that people use two strategies to localize smells: comparing the odor intensity between subsequent sniffs and comparing the odor intensity at the two nostrils during single sniffs.
"This is an innovative approach to teasing out what olfactory abilities humans actually have," says Gordon Shepherd, a neuroscientist at Yale University. It's assumed that after our primate ancestors started walking on two legs, their sense of smell became less acute, Shepherd says. The relatively small repertoire of olfactory receptor genes in primates compared to animals that kept their noses closer to the ground seems to support this notion. However, Shepherd says, the new study suggests that "if we go back on our four legs and get down on the ground, we may be able do things we had no idea we could do."
