Unboiled Frog Friday

You’ve heard the story many times; if you drop a frog in boiling water it’ll jump out, but if you raise the temperature slowly it will stay there until it dies. It’s a very useful metaphor for the way people can habituate to slowly worsening situations.

It’s also a true story. Frogs will indeed behave just that way – if you first remove their brains!

The experiment was done (in 1869) to find out if the reflex to escape from heat was activated in the brain or the spinal cord. A contemporary summarized the experiment and its results in an 1873 article in Nature:

“Goltz observed that a frog, when placed in water the temperature of which is slowly raised towards boiling, manifests uneasiness as soon as the temperature reaches 25° C., and becomes more and more agitated as the heat increases, vainly struggling to get out, and finally at 42° C., dies in a state of rigid tetanus. The evidence of feeling being thus manifested when the frog has its brain, what is the case with a brainless frog? It is absolutely the reverse. Quietly the animal sits through all successions of temperature, never once manifesting uneasiness or pain, never once attempting to escape the impending death.”

Goltz also touched the back of the brainless frog with a drop of acid and it instantly wiped the irritated spot with its leg, showing that the spinal cord can initiate complex reflex actions without the brain being involved. I don’t know if the spinal-cord-only coordination is sufficient to allow the decerebrated frog to actually jump out of already-boiling water if dropped into it (and I have no intention of performing the experiment myself), but a brainless frog will at least flinch at sudden discomfort, yet will placidly accept slowly increased temperatures… however, whole and healthy frogs will not.

So next time someone tells the ‘How To Boil A Frog’ story, be sure to jump in at the end with “Yeah – if the frog has no brain!!

You know, it even makes a better metaphor that way.


~ by B.T. Murtagh on July 24, 2009.

3 Responses to “Unboiled Frog Friday”

  1. […] the frogs let themselves be boiled slowly only if you Beckify […]

  2. I have never understood the need to subject a frog to something like boiling it slowly alive to figure out something that could easily have been figured out by the “scientist” putting his own hand in a pot of cold water and raising the temperature to a boiling point. “Gee, the water gets so hot I can’t keep my hand in it. I wonder if the same thing happens to a frog.”

    • Well, the question is whether the trigger to jump out originates in the brain or in the spinal cord. Unless the scientist were willing to have his brain removed for that part of the experiment that wouldn’t really work, and the process of writing up the paper would be severely compromised.

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