If you turn up the heat on a frog in water so slowly it doesn’t notice, will it eventually boil alive?

March 9, 2012

Dear Cecil:

This is an old one, and I'm surprised it didn't turn up when I did a search on your site. It has to do with boiling frogs. Goes something like this: If you tossed a frog into already-boiling water, it would leap out. But a frog placed into a pan of water with a low flame under it will slowly be boiled alive, the temperature change being too subtle for the frog to notice. This is exactly what is occurring today with the breakdown of moral values. The boiling bubbles are rising all around us, and few people realize what is taking place.

Cecil replies:

We were glad to get your letter, James, for three reasons: (1) We feel it’s our sacred duty to fact-check convenient parables, miracles, etc. No disrespect, but if we’d been on hand in a certain Middle Eastern locality 2,000 years ago, that bit with the loaves and fishes would have gotten more scrutiny than it did. (2) The story behind this much-told tale is so bizarre it’s a column all by itself. (3) Best of all, here was an experiment screaming to be done.

I looked at Una. She emphatically shook her head.

“But Una,” I said. “We’re the Straight Dope. We’re not like those above-it-all pussies at the New Yorker. We get our hands dirty.”

Una glared. “You don’t get your hands dirty,” she said. “I get my hands dirty. Look, I’ve painted my groin with alcohol to determine whether whiskey makes a good antiseptic. I’ve blasted bacon with a laser. I’ve drunk skunky beer to see if brown bottles prevent spoilage better than clear ones. But no way am I boiling any effing frogs.”

“You don’t actually have to boil them, Una. You just have to warm them up a little. I have total confidence that, crackpot legend notwithstanding, the frogs will jump out before any permanent damage is done.”

“So,” she retorted, “I only have to inflict a modest amount of torture on helpless research subjects, after which I’ve got a kitchen full of hot, pissed-off frogs.”

I conceded these practical difficulties. After further negotiation, Una agreed to a more limited research program at the library and came back with the following dossier:

1. The first reference to boiling frogs for science comes from a German researcher named Goltz, who in 1869 set out to discover — get ready for this — the location of the frog’s soul. For Goltz’s purposes, “soul” meant the part of the frog that would sense danger and impel it to escape impending death. So he immersed (a) a blinded but otherwise intact frog and (b) a decapitated frog in water, and gradually raised the temperature to see how each would react. At 77 degrees Fahrenheit the largely intact frog started to get uncomfortable. By 100 degrees it was desperately trying to escape the bath, and at 108 degrees it died. Aside from a few reflex twitches, the decapitated and basically dead frog was inactive, unsurprisingly to anyone but Goltz. The problem with this experiment, other than its being sadistic and ridiculous, was that the total heating time was only ten minutes, hardly a slow increase.

2. In 1872 another German named Heinzmann decided to conduct the definitive experiment on the subject. Heinzmann tested both brainless and blinded frogs and found that when the temperature was increased slowly enough — from 70 to 100 degrees over 80 to 95 minutes — the blinded frog would indeed die of heat exhaustion without a struggle.

3. In 1875 yet another German researcher, one Fratscher, confirmed Heinzmann’s results. Curiously, however, Fratscher and Heinzmann had the same supervisor. I make no accusations, but no one else has corroborated these astonishing findings. Then again, no one else has really tried.

4. 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.

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.)

So, do I think the story is a crock? Of course. Am I likely to prove this beyond a doubt? Absent a change of heart by Una, no.

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References

Foster, M. “On the Effects of a Gradual Rise of Temperature on Reflex Actions in the Frog” Journal of Anatomy and Physiology viii (1873): 45-53.

Fratscher, Carl. "Ueber continuirliche und langsame Nervenreizung." 1875.

Goltz, F. Beitrage zur Lehre von den Functionen der Nervencentren des Frosches, Berlin, 1869.

Hall, G.S., and Y. Motora, “Dermal Sensitiveness to Gradual Pressure Changes” American Journal of Psychology 1 (1887): 72-98.

Heinzmann, A. “Ueber die Wirkung Sehr Allmäliger Aenderungen Thermischer Reize auf die Empfindungsnerven,” Archiv fur die Gesammte Physiologie, Bd. VI (1872): 222-236.

Morgan, Ann Haven. “The Temperature Senses in the Frog’s Skin” Journal of Experimental Zoology 35 (1922): 98-130.

Scripture, Edward Wheeler The New Psychology London: Walter Scott, Ltd, 1897.

Sedgwick, W.T. “On Variations of Reflex-Excitability in the Frog, Induced by Changes in Temperature” Studies from the Biological Laboratory Baltimore, Johns Hopkins University, 1888.
 

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