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A friend of mine told me once about a documentary movie he saw some years ago. On this movie he saw scientists talking about particular experiment. This experiment involved rats and probably electrical traps. The rat had to get to the cheese, there were traps on the shortest route to it, and obviously it got shocked few times. What is interesting is that my friend says that when they took its offspring (probably born later) they avoided those traps.

I'm aware that its not how "genetic memory" works. Its not memory of individual, but of species (so it requires evolution). This is what I'm trying to explain to him, but he says "he knows what he saw".

Anyway maybe someone here is aware of such an experiment. I believe that he is wrong about something (or conclusions drawn where changed later), so I would like to find out more about it.

To sum up:

  • Its not Tryon's Rat Experiment
  • It involved: rats, traps (probably electrical), more then one path to cheese, rat's offspring and some sort of memory/learning amongst rats.
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This Nature Neuroscience paper published this week suggests that rats can pass on learned smell sensitivities to their F1 and F2 offspring. This is surprising stuff, so I imagine there will be a lot of close scrutiny and good conversation over the next few weeks. Here's a nice summary of the results from a National Geographic blog. –  Oreotrephes Dec 2 '13 at 18:43

2 Answers 2

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The phenomenon you're talking about was a fad in the 60's, called 'interanimal memory transfer'. It started out when James McConnell performed a later-discredited experiment in which he found that if you chopped up flatworms which had been exposed to some stresses, and fed them to other unexposed flatworms, the unexposed worms became wary of the source of stress quicker after eating their dead companions. He jumped to the conclusion that a 'memory molecule' was being transferred, and that the cannibal worms gained the food worms' memories of the stress.

People then started looking to see if they could:

  1. repeat the experiments
  2. find the same phenomenon in other animals

In the first case, nobody could replicate the experiments in worms, but because McConnell was such a PR genius he managed to convince the public that his results were valid (see Rilling, 1996 for more on this).

In the second case, Frank et al. (1970) and others tried working with rats - I think this is the experiment you're talking about in the question. They found various interesting results including that if you trained rats to run through a maze by using particularly stressful negative reinforcement (like electrocution), then those rats' children would be able to learn the new maze much faster. However, Frank et al. didn't make the same mistake as McConnell - first of all they wondered if the parent rats might be leaving a scent trail. So they used duplicate mazes with the exact same design, putting the children into clean mazes. The children of adults who had already learned the maze continued to outperform the control rats - the explanation was not scent trails.

Next they wondered whether it might be that the second generation rats had been born with a higher wariness as a result of the stress their parents suffered; i.e. it could be a hormonal transfer from mother to child (e.g. cortisol, the stress hormone).

Frank et al. tested their hypothesis by torturing some rats for a while (rules about animal welfare were not strict in the 70's). They would lock some rats in a small jar and bash them about for a long time, then kill them, chop them up, and take out their livers. They fed the livers to other rats, and found that after eating the livers the other rats learned the maze much faster. They interpreted the results in what now seems a sensible light: the stressed rats were producing high concentrations of a stress-signalling molecule. When those rats either had children or were fed to other rats, they passed on high doses of the stress molecule. This raised the alterness and wariness of the receipient rats so that they were much quicker to learn which parts of the maze were dangerous.

There is no evidence that the child rats actually 'remembered' the maze - they still had to find their way around, but they were extremely wary of the electrocution plates and so avoided them, finding the safest way to the end. This is not a case of genetic memory.

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+1 nice, interesting, detailed answer. –  Luke Jul 12 '12 at 8:55
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That was probably part of the fad to test Lamarckian ideas, wasn’t it? –  Konrad Rudolph Jul 19 '12 at 12:29
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@KonradRudolph yeah I think that whole thing was started as a result of McConnell's charade. I came across a reference to this when reading Carl Sagan's Demon Haunted World the other day, where he cited it (the flatwork memory thing) as an example of high-publicity pseudoscience. –  Richard Smith Jul 23 '12 at 11:32
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It also inspired a scene in THX1138 (early George Lucas film) where children are being fed their lessons through an IV bottle. –  shigeta Aug 4 '13 at 13:41

This is somewhat unrelated, and for that, I apologize, but I find it truly fascinating, and I believe you will too.

Zebra finches are a song bird that have become a popular model organism for behavioral research. They have a very stereotypical pattern for song learning: at about 70 days after hatching, the baby male song bird starts to listen to his father's song, copy it, practice it, and ultimately learn it. Female birds do not have a courtship song to learn.

Interestingly, if the baby male bird does not learn their father's song, they end up just kind of screeching, and never singing a song. This, in nature, makes them unable to court a female.

But in the lab, this research group did an experiment, where they took these screeching males, let them grow to adulthood, then teach their child as best as they can. The child, wanting to learn a song, takes what it can from the father. After 4 generations of this, the group was able to get de novo song production from these birds.

Unbelievable!

De novo establishment of wild-type song culture in the zebra finch - Fehér et al. - Nature, 2009

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Very interesting! I have not had the time to read through the article yet, so I do not know whether they address this, but I wonder what happens if then you expose those 4th generation birds to birds that sing normally. Who would they choose? A screeching one or a singing one? –  nico Aug 4 '13 at 12:20

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