# Do rats swim 240 times longer after being saved from drowning?

During a study at Harvard in the 1950s, Dr. Curt Richter placed rats in a pool of water to test how long they could tread water. On average they'd give up and sink after 15 minutes. But right before they gave up due to exhaustion, the researchers would pluck them out, dry them off, let them rest for a few minutes - and put them back in for a second round. In this second try - how long do you think they lasted? Remember - they had just swam [sic] until failure only a few short minutes ago... How long do you think? Another 15 minutes? 10 minutes? 5 minutes? No! 60 hours! That's not an error. That's right! 60 hours of swimming.

That seems like a rather insane claim to me. The idea that rats would only swim 1/240th their capability because they lacked hope of rescue.

Is this the right reading of the study? Did this ever happen?

• I think the answer is in On the Phenomenon of Sudden Death in Animals and Man. Apr 3 at 16:22
• @Laurel I used that to write an answer, thanks. Apr 3 at 17:25
• How exactly did they pluck them out right before they gave up due to exhaustion? Sure, they know the average amount of time until each rat gives up but that's just an average. How do they know the exact moment a given rat will give up so that they can pluck them out right before that? Apr 4 at 9:32
• I'm actually more interested in the claim that rats can swim for 60 hours. Regardless of the sudden drowning, I wouldn't think rats have enough stamina or endurance to keep going that long. Apr 5 at 3:04
• I'd imagine a rat that didn't get saved from drowning doesn't swim that often :-( Apr 8 at 15:52

# TRUE (kinda, it's complicated)

EDIT: To address Jack Aidley's comment: The physiological measurements mentioned in the paper, which indicates that some rats will die before they even enter the water, shows that there is more going on than simple drowning while searching for a way to escape. The behavior of searching below the waterline to escape is reasonable, but it does not account for the increase in heart rate, followed by a slow decline, that occurs whether or not the rat is in the water, as well as the sudden death of these "un-drowned" rats.

Also, in reply to the revisions in evan-carroll's answer, I'm glad that has led to a better answer and discussion overall. For now, I will just say that it's true that certain conditions led to sudden death and quick drowning for the wild rats, and that they could be conditioned to swim much (even 240 times!) longer. So the answer to the title is TRUE. Whether they have the notion of "hope" as physiologically measured in the actual paper is harder to conclude. The physiological evidence and reasoning presented in the paper is tough to follow, and may need further research.

Reading the answer from evan-carroll led me to the Wikipedia on the author. It gives an interesting quote from the paper. You can the see original on page 6 of the pdf cited both here and in Wikipedia.

Richter is quoted widely for his drowning rat experiments,[8] where rats would drown in a fairly short time without attempting to swim. But if rats had repeated experiences of rescue (or of being held briefly and then freed) they "do not die", and "show no signs of giving up". As described in the paper:

Support for the assumption that the sudden death phenomenon depends largely on emotional reactions to restraint or immersion comes from the observation that after elimination of the hopelessness the rats do not die. This is achieved by repeatedly holding the rats briefly and then freeing them, and by immersing them in water for a few minutes on several occasions. In this way the rats quickly learn that the situation is not actually hopeless; thereafter they again become aggressive, try to escape, and show no signs of giving up. Wild rats so conditioned swim just as long as domestic rats or longer.

This has been interpreted as an argument for the importance of hope and recirculates on the internet regularly.

Although the study does consider the effect of trimming rats, there is a mention about how rescuing the rats (whether wild or domesticated) will affect their behavior.

Note: Interesting enough there is a Medium article published around same time as this question that features an AI research assistant just for this paper!

• Although this correctly describes the claims of the paper, I'm not sure the paper actually supports this conclusion. Read the bit where it describes the sudden death behaviour "The first rat swam around excitedly on the surface for a very short time, then dove to the bottom, where it began to swim around nosing its way along the glass wall. Without coming to the surface a single time, it died 2 minutes after entering the tank. Two more of the twelve domesticated rats tested died in much the same way". This is the only description, it does not say whether the wilds behaved the same... Apr 4 at 13:50
• ... in my opinion there is another interpretation of this behaviour. Rather than "giving up", the rats - correctly assessing that they were trapped - persisted in seeking escape by desperately searching below the waterline. Apr 4 at 13:52
• @EvanCarroll the quote within the quote is copied from Wikipedia, yes. But it's originally from the last paragraph on the sixth page of the actual paper. Apr 5 at 1:44
• @JackAidley I think that's a reasonable interpretation assuming that the wild rats behaved similarly. However, it seems that some rats were dying even prior to exposure to water. It seems that the water is contributory to sudden death, but not essential. Consider this quote from the paper: "However, some of the wild rats died simply while being held in the hand; some even died when put into the water directly from their living cages, without ever being held. The combination of both maneuvers killed a far higher percentage." Apr 5 at 1:52
• @nathansit: The comments section of SE is not the place for extended discussion of a scientific paper, so I'll leave it here :) Apr 5 at 7:36

# The claim is without evidence.

The statement is present in the conclusion but it is NOT substantiated by the data. The study was over clipping rats wiskers and triming their hair in between wild and domesticated rats. The study is On the Phenomenon of Sudden Death in Animals and Man.

# Study

## Study

Using electric clippers, the whiskers and hair of the facial area were trimmed before the animals were placed in water at 95 ° F., a temperature at which most intact, control rats swim 60 to 80 hours.

(This is to say without the trimming rats swam 60-80 hours)

## Domesticated rats

The first rat swam around excitedly on the surface for a very short time, then dove to the bottom, where it began to swim around nosing its way along the glass wall. Without coming to the surface a single time, it died 2 minutes after entering the tank. Two more of the twelve domesticated rats tested died in much the same way; however, the remaining 9 swam 40 to 60 hours.

That is to say, of the domesticated rats with trimmed facial hair three quickly died and 9 swam for 40-60 hours (control was 60-80 hours wo/ trimmed facial hair).

## Hybrid rats

Five of 6 hybrid rats, crosses between wild and domesticated rats, similarly treated, died in a very brief time.

## Wild Rats

We then tested 34 clipped wild rats, all recently trapped. These animals are characteristically fierce, aggressive, and suspicious; they are constantly on the alert for any avenue of escape and react very strongly to any form of restraint in captivity. All 34 died in 1-15 minutes after immersion in the jars.

That is to say, wilds rats with trimmed facial hair die in 1-15 minutes because they panic.

# Conclusion and potential confusion

The conclusion from the paper, is this

From the results we concluded that trimming the rats' whiskers, destroying possibly their most important means of contact with the outside world, seemed disturbing enough, especially to wild rats, to cause their deaths.

The confusion probably comes from this,

At present it appears that of all these factors, two are the most important: [the restraint involved in holding the wild rats, thus suddenly and finally abolishing all hope of escape; and the confinement in the glass jar, further eliminating all chance of escape and at the same time threatening them with immediate drowning.

"Eliminating hope of escape and chance of escape" isn't exactly scientific wording. Who knows how a rat conceives hope, and how they assess chance; but, they were never given any notion of hope because no rats were rescued and re-experimented to produce the data. Each trial was done with new rats. So all rats were equally without hope and chance of escape. The only variable was the rats genetics (wild or domestic). The group that swam longer did NOT do so because they were taught they'd be rescued and swam longer with hope (expectation) of rescue. They swam longer because they were domesticated rats and NOT wild rats.

## Bizarre out of place statement

To make this paper even more bizarre the author says,

"Support for the assumption that the sudden death phenomenon depends largely on emotional reactions to restraint or immersion comes from the observation that after elimination of the hopelessness the rats do not die. This is achieved by repeatedly holding the rats briefly and then freeing them, and by immersing them in water for a few minutes on several occasions. In this way the rats quickly learn that the situation is not actually hopeless; thereafter they again become aggressive, try to escape, and show no signs of giving up. Wild rats so conditioned swim just as long as domestic rats or longer."

However, THERE IS ABSOLUTELY NO EVIDENCE FOR THIS CLAIM. It is not data. I have no idea how they determine this. There is no methodology. And we have no information about the trials. This is an absolutely extraordinary claim that the publication provides absolutely zero evidence for. Hence, I would dismiss it entirely. It is certainly unrelated to the remaining eight pages.

• For domesticated rats, you've quoted and bolded the wrong bit: that section is saying that untrimmed rats swim for 60 to 80 hours. The information about domesticated rats starts in the next sentence. It says that of twelve domesticated rats, three died extremely quickly (like five of the six hybrid rats and all of the thirty-four wild rats) and nine swam for 40 to 60 hours -- which is in the same ballpark as, but still less than, untrimmed rats. Apr 4 at 4:30
• "The conclusion from the paper, is this" -> No, it is not. The very same paragraph continues: "From the results we concluded [... etc. etc.]. However, when we began analyzing the various steps involved in transferring the fierce, wild rats from their cages to the water jars without the use of any anesthetic, it became obvious that a number of other factors had to be taken into account [...]" Apr 4 at 8:25
• "no rats were rescued and re-experimented" -> On the contrary (once again), the study says exactly the opposite: "in order to measure the maximum swimming time, we now try to free the rats of all emotional reactions to restraint or confinement by successively exposing them to these situations and freeing them several times beforehand. In this way we have succeeded in eliminating most of the individual variations and are now obtaining quite constant, reproducible, endurance records for both domesticated and wild rats." Apr 4 at 8:40
• @EvanCarroll It seems you have chosen to ignore all claims in the paper that are not supported with specific data, even if the author presented those claims as factual. The way you've gone about this has obviously caused a fair amount of confusion. You're going so far as to say that the author is lying about steps that were performed and observations that were made, when those steps/observations are not supported with specific numbers. I understand where you are coming from, but you really should make your position clear at the beginning of your answer. Apr 5 at 0:28
• @EvanCarroll As your answer is written now, it initially appears that you have simply cherry-picked phrases from the paper to support a conclusion that deliberately misrepresents what's written in the paper. Adding a little bit of explanation/example, e.g. "The author says 'Wild rats so conditioned swim just as long as domestic rats or longer', but provides no numbers or data to support this claim" would help to avoid confusion, particularly for readers who aren't used to reading scientific papers, or who are skimming the paper and miss the lack of data. Apr 5 at 0:33