[prngl]

If we go a bit old-school on AI and reason in the "connectionist" framing:

Let's say neural memories are encoded in some high-dimensional vector space.

And so memory recall is an associative process that entails constructing a query vector and issuing it across the neural memory space.

And the brain is constantly learning, and that learning entails some changes in the structure of the high-dimensional memory space.

And let's say that re-encoding of a neural memory happens upon recall, and only upon recall.

Then it could be that all experience is in fact stored, but because of changes due to learning, those memories become inaccessible. The machinery constructing query vectors has updated its structure enough that its encoding of those query vectors is sufficiently dissimilar from the encoding of the stored memory vectors (which use the encoding from the last recall).

[spwa4]

Also known as "catastrophic interference" or "catastrophic forgetting" ... No all that catastrophic unless it balloons, but it's a name that stuck.

https://en.wikipedia.org/wiki/Catastrophic_interference

[dist-epoch]

We know there is massive prunning and "dropout" of brain connections during young age.

[tralarpa]

> The machinery constructing query vectors has updated its structure enough that its encoding of those query vectors is sufficiently dissimilar from the encoding of the stored memory vectors (which use the encoding from the last recall).

Wouldn't that result in very bizarre memories instead of no memories?

[phantompeace]

Not unless the brain does filtering (something we know for sure it does - psychedelics mess with this filter). I may be completely off the mark though

[mystified5016]

The brain is sufficiently complex that I'd expect gross distortions will get swept under the rug. You'd get either lightly distorted memories (dad is 18ft tall, mom's face is wrong, favorite toy lived in this spot instead of that one) or nothing at all. If a memory is totally corrupted, your brain won't give it to you because it doesn't pass your perceptive filters.

Children believe a lot of silly things that they "grow out" of thinking.

How sure are you that your childhood memories are accurate? How sure are you that you aren't simply conditioned to ignore distorted childhood memories?

[naderraider]

this appears to be more or less what happens. (https://www.science.org/doi/10.1126/science.ade6530)

[memhole]

On re-encoding memories as well:

https://www.jneurosci.org/content/32/35/12144

Oops, someone else posted this further down too. Great minds think alike!

[qudat]

I like this while including the brain regularly does “cleanup” of connections that it deems unnecessary and removes them.

[username135]

I like this one

[perfmode]

Cool

[suddenlybananas]

Doesn't really explain why it happens universally and why this doesn't happen after other major changes in lifestyle (people who move to a radically different country don't lose all memories of their life beforehand).

[llamaimperative]

From the brain’s POV even a radically different country is like 99.9% the same as anywhere else on earth.

[suddenlybananas]

Sure, but is the difference between being 2 and 4 really that profound? It's not like the memories that are lost are just of the womb.

[ecshafer]

Have you spent a lot of time with children?

My 2 year old went on a mental breakdown of a temper tantrum last night because she saw an apple on the tv, decided it meant she wanted an apple, and couldn't understand why she could not have an apple despite seeing one on the tv just then! A toddler is still trying to understand how reality itself works.

A 4 year old knows that jumping off of the stairs onto tile is going to hurt. A 4 year old understands the apple on the tv is an apple on the tv and is not a physical apple in the house.

They are so far apart.

[suddenlybananas]

Obviously a 4 year old is much more together than a 2 year old. But we're talking about a fundamental difference so great that no memories can be preserved. That's a high bar.

[llamaimperative]

Uhhh yes.

Age 2: Can point to their own body parts; hold something in one hand while doing something with the other hand

Age 4: Changes behavior based on where you are; can draw a person with more than 3 distinct body parts

There's a huuuge amount of learning that happens through this period. Your brain is learning things like 3-dimensional space, temperatures exist and I don't like some of them, I-have-two-arms, things fall when dropped, I must engage my big toe to stay upright while walking, other people appear to have feelings, other people appear to believe that I appear to have feelings.

And in any case, the difference between 2 and 4 is only relevant to the question of whether a 4 year old can remember being 2, not what this article is about, which is adults not remembering being <4.

[suddenlybananas]

>There's a huuuge amount of learning that happens through this period. Your brain is learning things like 3-dimensional space, temperatures exist and I don't like some of them, I-have-two-arms, things fall when dropped, I must engage my big toe to stay upright while walking, other people appear to have feelings, other people appear to believe that I appear to have feelings.

Many of those things are completely innate. Walking for example, while people use the word "learn" in casual speech, is something that is innate. I just don't think the original comment is well-grounded in what we know about infant's cognition. And in any case, a 2 year old definitely understands 3D space.

[llamaimperative]

... walking absolutely must be learned... They will automatically learn it without explicit teaching but indeed it must be learned. A child prevented from standing or walking for 5 years and then stood on their feet for the first time will not be able to walk.