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传说的康奈尔大学19世纪“温水青蛙实验”与实证的21世纪“青蛙跳高实验”

已有 2116 次阅读 2020-7-13 09:50 |个人分类:社会观察|系统分类:海外观察

                 ——康奈尔大学19世纪“温水青蛙实验”可能并不存在,实验故事可能源自一则德国传言

                 ——康奈尔大学21世纪2019年的“青蛙跳高实验”倒是正式发表、有理有据的科学实验              

                 ——蛙类耐受酷寒的特殊生理机制受到重视,对人类器官保护与移植具有重要借鉴意义

      所谓康奈尔大学19世纪的“温水青蛙实验”,中英文网页随处可见。然而,澳大利亚的科学节目类主持人、30多本科普著作的作者卡尔博士(KARL KRUSZELNICKI)指出:“所谓温水青蛙实验的故事或许源自E.W.Scripture之口,他在1897年撰写了《新心理学》,在该著述里了引用了所谓较早的德国研究成果(陈昌春注:或许未注明出处):“如果水加热得足够慢,活青蛙实际上可以在温水里保持安定; 在一个实验中,温度以每秒0.002摄氏度的速度升高,过了2.5小时发现青蛙并没有不安,而是死了。”(详见附4)

      从证伪的角度来看,19世纪离现在不算太远,如果康奈尔大学19世纪的“温水青蛙实验”确实进行并得出结果,通常会以书面的形式记载及发表。然而,似乎并没有这样的书面记录或线索存在。

      21世纪的2019年,该校有研究团队进行了包括“青蛙跳高实验”在内的一些水生动物及两栖动物跳高试验(详见附8)。据称,青蛙可以跳出自己身长的5-10倍的高度,目的主要是捕捉食物(Mid-sized animals, such as frogs or archer fish, may jump five to close to 10 times their body length, mostly to catch prey. )

      关于蛙类,有文章分析了树蛙为何具备耐受酷寒、笑傲冰霜的特殊生理机制(《Cryobiology: Frozen Wood Frogs and Adaptations for Survival》,https://owlcation.com/stem/Frozen-Wood-Frogs-and-Adaptations-for-Survival),并对人类与蛙的生理特性进行了对比,指出蛙的耐寒能力与机理对人类的器官移植等具有重要的借鉴意义(Understanding how the frog's body responds to temperatures below and then above freezing may help us improve the cryopreservation (preservation at low temperatures) of human cells, tissues, and organs. These need to be preserved in excellent condition so that they can be transplanted into the patients that need them. Improving the preservation of organs would be especially helpful. At the moment, these are cooled but not frozen, which limits their availability to patients who need them. The organs eventually die unless they are frozen. Freezing and thawing are much more successful for small items such as eggs, sperm, and embryos than for large items such as organs. Frozen organs are damaged by cracking during the thawing process.)。

附1:https://baijiahao.baidu.com/s?id=1620986832044496586&wfr=spider&for=pc

                          温水里的青蛙真的会坐以待毙吗?科学实验告诉你寓言不可信

                                                                 奇点先驱 发布时间:18-12-27

      关于青蛙,还有一个耳熟能详的故事,那就是温水煮青蛙。一开始大家都认为这是中国的传统故事,实际上这个故事是从美国传过来的,而且它还是来源于一项科学实验。在1894年,美国康奈尔大学的科学家用青蛙做了一个实验,看看青蛙是如何应对环境变化的。他先是在一个器皿中装满了温水,然后将青蛙放进去,青蛙一碰到温水就立马跳了出来。然后他把温水换成冷水,将青蛙放进去,再逐渐加热冷水。他惊讶地发现青蛙对温度变化竟然毫无反应,一点挣扎都没有,最后青蛙在水温逐渐上升的过程中就被煮死了。我们姑且不探讨这个实验的真实性,这个实验本身就很有寓意。中国人也经常引用这个故事来劝告别人,不要对自己所处的环境一点察觉都没有,否则最后将大祸临头。虽然这是一个十分有寓意的实验,但如果追究其科学性和真实性的话,青蛙是不会在逐渐升温的水中坐以待毙的。因为我国有一所中学曾经就做过类似的实验,实验人员将青蛙先放在一锅冷水里面,锅中放有一根温度计。然后再慢慢给水加热,一开始青蛙确实毫无反应,但是当温度上升到了40摄氏度以上后,就有青蛙开始跳出锅了。等到温度上升到50摄氏度,锅里的青蛙全部都跳出去了。

附2:https://www.zhihu.com/question/23642982

                                                温水煮青蛙理论是真的假的?有人做过验证么?

                                                                            作者:知乎用户

                                                                         温水煮青蛙 百年实验考

奥克拉何马大学的动物学教授霍奇森选定的加热速率,是每分钟2华氏度,也就是差不多1.1摄氏度。霍奇森发现,到了一定温度以后,青蛙会开始躁动不安,试图逃离这个环境,如果装载的容器允许,青蛙还是会跳出来的。基于此,霍奇森宣布,温水煮青蛙的故事是错误的。
1872,一个叫做亨滋曼的宣布,如果你加热的速率足够低,那么,青蛙并没有跳出来的打算。1875年,这个实验还被另外一个人证实。
两个实验矛盾吗?哥而茨与亨滋曼的实验的区别是加热的速度不同。
这些“煮”青蛙的实验目的都是考察温度和神经反射性的关系。在较快的加热速率下,青蛙能跳出来,原因很好理解:热刺激引起了青蛙的应激反应——跳走。而在较慢升温过程中,由于类似“感觉适应”的原因,持续细微的温 度变化使得青蛙适应了这种刺激,反射应激性降低,直到达到可耐受的临界高温,无法逃生。

结论: 在温度变化明显的情况下,青蛙可以迅速跳出。而当水温变化很微小的时候,青蛙就难于察觉,而失去逃生的机会。“温水煮青蛙”故事背后的依据是有一定道理的,只不过能煮死青蛙的这个升温条件和我们一般理解的“煮”不太一样。

       @苏莉安 所做的实验和霍奇森教授所做的实验是一样的,但并不能因此判定这个理论是假的。如同离开剂量谈毒性都是耍流氓一样,忽略水温的加热速度而得出结论的都是耍流氓。

附3:https://www.jqknews.com/news/160152-Do_you_know_theres_nothing_wrong_with_boiled_frog_in_warm_water_Are_frogs_really_that_stupid.html(网易科学)

Do you know theres nothing wrong with boiled frog in warm water? Are frogs really that stupid?

                                                                      2019-03-28  

Production | Netease Science and Technology Know or not column group (public number: tech_163)

Many people have heard the story of boiled frogs in warm water, but is it true that it has been told for hundreds of years? Are frogs really that dumb?

The phrase boiled frog in warm water comes from a boiled frog experiment conducted by scientists at Cornell University in the late 19th century. When scientists plunged frogs into 40 degrees Celsius water (not boiling water), they could not stand the sudden high temperature and jumped out of the boiling water to escape. When scientists put frogs in containers filled with cold water and then heated them slowly (up 0.2 degrees Celsius per minute), the results were different. Frogs, on the contrary, are comfortable in the water because of the comfortable water temperature at the beginning. When the frog found that he could not stand the high temperature, he had enough energy and was boiled to death in hot water unconsciously.

This story is implied by people that changes in the general environment can determine your success or failure. Too comfortable environment often contains danger and perceives small changes in trends. You must stop and think from different angles. Learning is the best way to discover changes.

For example, people are often used in the workplace, many people can easily complete their work in their own work, the work is not challenging, and lack of motivation for progress, slowly being worn off the spirit, motivation for progress and innovation, once the company changes, it may be abandoned.

But is this story, which has been told for hundreds of years, true? Are frogs really that dumb?

It was reported on the Internet that a female biology teacher organized the whole class to do the experiment of boiling frogs in warm water. When the water temperature was heated to 60 degrees Celsius, some frogs began to jump out of the water. When the water temperature continued to rise to 65 degrees Celsius, all the frogs in the container jumped out. This proves that Cornell University scientists are wrong.

In fact, Hodgson, a professor of zoology at the University of Oklahoma, did a similar experiment. Hodgson studied the response of different types of amphibians to temperature. Frogs belong to amphibians. Amphibians are cold-blooded and thermophilic animals, and their body temperature will be adjusted with the temperature of the environment. Hodgsons research is about the maximum temperature that amphibians can tolerate.

Hodgsons chosen heating rate is 2 degrees Fahrenheit per minute (about 1.1 degrees Celsius). At a certain temperature, the frog starts to get restless and tries to escape from the environment. If the container is loaded, the frog will jump out. Based on this, Hodgson declared that the story of boiling frogs in warm water was wrong.

When the story of boiled frog in warm water was considered false, there was another experiment called Huntsmans experiment. 1872, a publication called Huntsman, if you heat at a low enough rate, the frog has no intention of jumping out. Huntsman used 90 minutes to heat water from 21 degrees Celsius to 37.5 degrees Celsius, with an average heating rate of less than 0.2 degrees Celsius per minute. No abnormal behavior was observed in frogs. The critical high temperature (CTM) that frogs can tolerate is about 36 - 37 degrees Celsius. If heated to 37.5 degrees Celsius, the frog has lost its ability to jump up even if it does not die immediately, and death is not far from it.

Therefore, frogs can jump out quickly when the temperature changes obviously. When the water temperature changes very slightly, frogs are hard to detect and lose the chance to escape. So the story of boiled frogs in warm water has some truth.

Whatever the authenticity of the experiment, the implication of boiling frogs in warm water still needs our vigilance. The worst case is not that we are in a bad environment, but that we gradually degenerate without knowing it. When we finally wake up, it is too late.

Netease Science and Technology Know or not column, curious about the world, with you to explore the unknown.

Pay attention to Netease Technological Micro-Signal (ID: tech_163), send Know or Not, you can see all the knowledgeable manuscripts.

Source: Editor in charge of knowledge: Qiao Junjing_NBJ11279

附4:https://www.conservationmagazine.org/2011/03/frog-fable-brought-to-boil/

FROG FABLE BROUGHT TO BOIL

                                                                            By Dr. Karl S. Kruszelnicki

If you plunge a frog into boiling water, it will immediately jump out. But if you place the frog into cool water and slowly heat it to boiling, the frog won’t notice and will slowly cook to death. So claims the myth. Indeed, everyone—from corporate consultants to politicians to environmental activists—cites the frog fable as proof that people often don’t see change happening and cannot deal with it in the aftermath.

So how did this myth begin? Maybe it arose because frogs are cold-blooded. We humans are warm-blooded: our internal thermometers measure the local temperature, and then we shiver or sweat to maintain a body temperature of around 37 degrees Celsius. But a cold-blooded frog maintains the temperature of its immediate environment. Perhaps somebody once wrongly thought that this meant frogs had an inferior or inadequate thermometer.

Or perhaps the story began with E.W. Scripture, who wrote The New Psychology in 1897. He cited earlier German research: “. . . a live frog can actually be boiled without a movement if the water is heated slowly enough; in one experiment, the temperature was raised at the rate of 0.002 [degrees Celsius] per second, and the frog was found dead at the end of 2.5 hours without having moved.

Well, the numbers just don’t seem right. If the water comes to a boil, that means a final temperature of 100 degrees Celsius. In that case, the frog would have to have been put into the water at 82 degrees Celsius. Surely, the frog would have died immediately. Scripture also wrote that the frog was found “without having moved.” How do you convince a frog not to move for more than two hours?

Then there’s the issue of the real-life behavior of frogs. First, a frog cannot jump out of boiling water. Remember the last time you dropped some egg white into boiling water: the proteins coagulated into a mess of thin, white strands. Unfortunately, the proteins in the frog’s skinny legs would do the same thing. So the frog in boiling water could not jump anywhere. It would die a nasty death.

Dr. George R. Zug, curator of reptiles and amphibians at the American Museum of Natural History in New York, and Professor Doug Melton of Harvard University both agree on this point.

Second, a frog would notice the water getting hot. Dr. Victor Hutchison, a herpetologist at the University of Oklahoma, has dealt with frogs throughout his professional life. Indeed, one of his current research interests is “the physiological ecology of thermal relations of amphibians and reptiles.” Professor Hutchison states, “The legend is entirely incorrect! The ‘critical thermal maxima’ [the maximum temperature an animal can bear] of many species of frogs have been determined by several investigators. In this procedure, the water in which a frog is submerged is heated gradually at about 2 degrees Fahrenheit per minute. As the temperature of the water is gradually increased, the frog will eventually become more and more active in attempts to escape the heated water.”

So real-life experiments show that the frog-in-boiling-water story is wrong. If only this fact could make it into real life, too. ❧

DR. KARL KRUSZELNICKI is an Australian Science broadcaster and the author of 30 popular science books. For more info, visit: www.drkarl.com. This article was adapted from his book “It Ain’t necessarily So… Bro”

附5:https://edition.cnn.com/2019/02/25/health/climate-change-boiling-frog-study/index.html

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附6:https://lethbridgeherald.com/commentary/letters-to-the-editor/2019/11/29/like-a-frog-in-a-pot-of-warm-water/

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附7:http://awesci.com/the-old-tale-of-a-boiling-frog/

                                                          The Old Tale of a Boiling Frog 

                                                                BY ANUPUM PANT

Background

The Frog in a pot is a very popular anecdote and you probably know about it. Still, if you don’t, it is about a frog that rests easy in a pot of water that is warmed slowly. Frogs normally won’t go into boiling water. They’ll jump out and keep themselves away from very hot water. But, if placed in a tub of water at normal temperature that is being heated slowly, according to the anecdote, they don’t react and end up getting cooked in the boiling water.

The story is used as a metaphor to tell a cautionary point about life. The moral of the frog story goes something like this – Letting small and seemingly harmless wrongs slip, could kill (or be bad for you).  It basically tells you to not be complacent about minor changes that usually seem harmless, but add up to something big/bad.

The video proof?

Scientifically, a bizarre video (not for the faint hearted) on Youtube claims to proves the frog tale. The guy in the video initially tries to put a frog in a pot full of boiling water. Of course it resists, and doesn’t go in. Later, when the frog is put into a pot full of water at normal temperature and is warmed gradually, the frog never tries to leave. It gets cooked in the boiling water. Just like the tale suggests.

Everything looks very convincing about the video experiment. Little details like placing the frog on a piece of insulator so that it doesn’t feel direct heat through the metal base, are also taken care of in the video. Also, the narrator sounds so convincing with all the science facts referring to how cold blooded animals react to temperature. They indeed do! I totally fell for it. Watch it below… 

The video cuts in between and the water which was put on flame before starts boiling suddenly after the cut. Or brains tend to skip video cuts. In the boiling water is something that looks like a dead/cooked frog. If you watched it till the end, the video shows you that the dead frog wasn’t a real one. No frogs were harmed in the making of the video. Good.

But, that completely nullifies the point this experiment tries to make. A fake rubber frog being cooked in boiling water doesn’t scientifically prove the tale.

The Science

Unlike us, who maintain a constant body temperature, the frog being a cold blooded animal, its body will react to its surrounding temperature and will try to match it. But real scientific experiments have never been able to prove it. According to a very old experiment that was done in the 1800s, where water was heated at 0.002°C per second, the frog was found dead at the end of 2½ hours. Why do you think would the frog sit still for 2½ hours?

Modern scientists reject the old experiment which seems to prove it. You could place your trust in the words of a Harvard professor, Professor Douglas Melton. He says:

If you put a frog in boiling water, it won’t jump out. It will die. If you put it in cold water, it will jump before it gets hot—they don’t sit still for you.

Victor H. Hutchison, Professor Emeritus of Zoology at the University of Oklahoma also said, “The legend is entirely incorrect!”

Moral: don’t believe everything you see on the internet.

Hit like if you learnt something today.

附8:https://news.cornell.edu/stories/2019/03/robot-biomimics-animals-leaping-water

                                     Robot biomimics animals leaping from water

                                                 Krishna Ramanujan   March 6, 2019    

By studying the mechanics that one-millimeter copepods employ to jump out of water, scientists could build robots that use similar jumping techniques for practical purposes.

A new study, published March 6 in the Journal of the Royal Society Interface, describes the patterns and parameters required for animals as varied as copepods (a kind of crustacean), frogs, fish, dolphins and whales to leap from water to air – a challenging task given that water is 1,000 times denser than air.

         

                                                   Sunghwan Jung/Provided

An orca jumping at SeaWorld in Orlando, Florida.

Research that breaks down exactly how aquatic animals get air time has been scarce – until now.

To experiment with such leaps, the researchers created a simple water-jumping robot. But the robot also has practical applications: If fitted with a sensor that detects polluted water, for example, an immersed device could jump when triggered, and transmit a signal to notify water managers of polluted areas. Compared to sending signals through water, transmitting signals through air is more efficient, cheaper and doesn’t require large equipment to transcend the air-water interface.

“The big picture is to try to understand how animals behave in nature,” said Sunghwan Jung, Cornell associate professor of biological and environmental engineering, and the paper’s corresponding author. “Animals have evolved millions of years to optimize their behavior and maximize their performance. From there, we can learn how to design a product or engineering system to perform better.”

Jung and colleagues identified a number of patterns when analyzing the jumping behaviors of species across five taxonomic groups. Small copepods can jump up to 20 times their body length, while larger animals, like whales, are lucky to get their whole bodies out of the water. “In small animals, jumping is strongly related to survival, so that’s why their performance is way better,” Jung said. “If they cannot jump high enough, then they will get killed.”

Mid-sized animals, such as frogs or archer fish, may jump five to close to 10 times their body length, mostly to catch prey. Large animals may jump to play, communicate or attract a mate, but no one is sure why whales and dolphins jump.

The researchers also created an equation to mathematically represent these jumping dynamics, which included an animal’s maximum jumping height, body length and the role of gravity as it exits the water. The equation quantifies the balance between how much power an animal has versus how much power it must expend to raise itself out of the water, which is affected by gravity and water drag.

While designing the robot, the researchers mimicked the quick clapping motion that frogs and copepods use to jump; frogs clap their hind webbed feet together and copepods clap two special antennae. Using a simple design, the robot includes a 3D-printed hinge with two flaps, like a door hinge, a rubber band and a tiny wire. When tripped, the wire frees the hinge to snap around in a clapping motion that propels the robot from the water.

The rudimentary biomimicking robot lacked the streamlined qualities of living animals, creating a lot of water drag. On the other hand, copepods, frogs and archer fish, for example, have streamlined bodies and exit the water without carrying much fluid with them. “Our robot cannot jump as high as an animal due to the entrained water or drag,” Jung said. In the future, the researchers will streamline the robot to make it more effective.

While animals are hard to control in such experiments, the robotic system gave the researchers control so they could experiment with wing lengths and tension, to better understand the forces at play.

Brian Chang, a former graduate student at Virginia Tech and now a researcher at Temple University, is the paper’s first author. Co-authors include researchers from the Seoul National University in Korea, Ecole Polytechnique Federale de Lausanne in Switzerland, Harvard University, and the Ecole Polytechnique in France.

The study was funded by the National Science Foundation and the National Research Foundation of Korea.



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