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It's commonly believed that a frog will not perceive a rise in temperature, and will boil alive. And, of course, if it were to be put in already-boiling water, it will immediately jump out.

Any truths to this?

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Here's my answer posted as a reply to the same question on Biology beta: biology.stackexchange.com/questions/1660/… –  rebeccabeckybec Jun 2 '12 at 20:49
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4 Answers

up vote 7 down vote accepted

No, they don't just hang out in the water until dead. If you think about it this doesn't make sense from an evolutionary standpoint. A frog evolved in an environment where water heats slowly, not where water is suddenly boiling (boiling water isn't terribly common in nature).

http://www.uga.edu/srel/ecoviews/ecoview021118.htm
http://www.snopes.com/critters/wild/frogboil.asp

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Looks like we need to find a new metaphor, then. –  skizeey Jul 25 '11 at 21:02
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If I do something for 3 hours, it will be 180 minutes. 180*0.002 = 0.36. Why will the frog die? Because of boring experiments? :) –  user unknown Jul 26 '11 at 2:14
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@user unknown, oops, it's actually .2C per minute...:) –  Thursagen Jul 26 '11 at 3:36
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"No, they don't. " They don't what? I do not understand to which part of question this relates. Also, would you mind blockquoting the sources? –  Suma Jul 26 '11 at 6:12
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@HamandBacon, have you a reference to prove that? Asking people to go off and boil live frogs might be considered a little unethical. –  Oddthinking Jul 26 '11 at 16:48
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Snopes tackled this myth and the answer is that this is untrue. Although older experiments support this, it's been pretty debunked by modern science.

Snopes quotes a Dr. Victor Hutchison, Research Professor Emeritus from the University of Oklahoma's Department of Zoology:

The legend is entirely incorrect! The 'critical thermal maxima' 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 2 degrees Fahrenheit [about 1.1 degrees Celsius] 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. If the container size and opening allow the frog to jump out, it will do so.

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The whole "debunked" meme is basically slanderous in science. It implies not just that the previous science was wrong, but that it was garbage and/or fraudulent to begin with. It's unnecessary rhetoric that degrades science, which is all about continual improvement, and can only happen by our predecessors being wrong in some way. Calling it "debunking" devalues the important work predecessors contributed. Science is about building on the past. Debunking is the politicization of science. –  Russell Steen Jul 25 '11 at 21:53
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Wow, I did not realize the word had such connotations. I always figured it just meant it was later proved wrong. –  TheEnigmaMachine Jul 25 '11 at 22:27
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@AgentKC - you are right. de·bunk/diˈbəNGk/Verb 1. Expose the falseness or hollowness of (a myth, idea, or belief) - sure, science improves, but it is blatantly obvious that for earlier scientists to claim this myth was true, there must have been something going on... –  Rory Alsop Jul 25 '11 at 22:40
    
Hmn... agreed that the answer could do a better job of quoting Snopes' argument. But the Snopes page itself looks reasonably well-referenced to me (not to mention, one could argue that the null-hypothesis is that frogs will notice, and therefore burden of proof would be on the folk-theory that they don't). –  Dave Jul 26 '11 at 9:43
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@Rory Alsop -- Dictionaries don't always cover current social connotations and implications of words. However in this case, at least some do if you don't cherry pick your definition: Via Dictionary.com, first definition -- "to expose or excoriate (a claim, assertion, sentiment, etc.) as being pretentious, false, or exaggerated". –  Russell Steen Jul 26 '11 at 13:33
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Dr Karl commented on the original German experiments:

Or perhaps the story began with E.M. Scripture in 1897, who wrote the book, The New Psychology. 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°C per second, and the frog was found dead at the end of two hours without having moved."

Well, the time of two hours works out to a temperature rise of 18°C. And, the numbers don't seem right.

On the other hand, while the Straight Dope is doubtful, it believes that the evidence could be better:

Getting back to boiling, modern commentators agree the results claimed by the German researchers are preposterous. However, no one to my knowledge has attempted to precisely replicate the earlier work, possibly because they haven’t read the studies, which are written in (duh) German. In the experiments I’ve come across, researchers have placed frogs in water and heated it relatively quickly till the frogs jumped out, failing to recognize that the point of the exercise was to heat the water gradually. (Typically the gas gets turned up at a rate of two degrees per minute, about six times faster than Heinzmann did it.)

They also claim that a similar experiment was done with crushing the feet of a frog:

On a related subject, psychologist Edward Scripture in 1897 noted a grisly experiment where a frog’s foot was clamped in a screw press that was tightened at about a thousandth of an inch per minute. Result: the foot was completely crushed without the frog showing any distress. Somewhat worryingly, the author wondered what could be accomplished using humans rather than frogs.

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Here's my answer, this time copy-pasted instead of linked, posted as a reply to the same question on Biology - Stack Exchange:

This answer belongs on Skeptics. Sorry to disappoint, but the "boiled frog" phenomenon is an "old folk warning". This essentially negates your original question altogether. Neither a cold-blooded animal (such as a frog) or warm-blooded animal will boil to death under the conditions implied by the warning (i.e. escape is permitted and water is heated very gradually).

1897 research by German scientist E. W. Scripture, upon which the fable may have first been based, has been deemed flawed by scientists:

From Scripture's 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."

According to Dr. Karl S. Kruszelnicki (Australian scientist): "[T]he 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."

According to Dr. Victor H. Hutchinson (Herpetologist and Zoology Professor at University of Oklahoma): "The legend is entirely incorrect! The 'critical thermal maxima' 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. If the container size and opening allow the frog to jump out, it will do so."

Whit Gibbons (University of Georgia) says that there is an important message behind the false legend:

So where does that leave us with the boiling frog as a metaphor for the human response to economic change or environmental degradation? Well, it's not true that you can induce a frog to willingly remain in boiling water by starting it off in cold water. But that does not diminish the truth of the message that the accumulation of imperceptible changes can have a significant effect on the economy and the environment. We need to be aware of what changes are occurring and to respond to them in a timely fashion. The metaphor lies in the frog's ability to escape from the container: if there's no way out, then the frog's fate is a foregone conclusion.

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