At what age does a child start retaining memories?

Memories are more likely to survive into adulthood around age 7, but anything truly significant or continuously experienced (special vacations, monthly visits to grandma's) can stay with them much longer.

Around age 7 "childhood amnesia" kicks in and they begin dumping huge patches of experiences that they haven't otherwise found critical to their day to day life.

Up until that point, they are sponging up gigantic (unfathomably large for you and I) amounts of information and will be able to recall the tiniest details that you and I would find inconsequential, because they don't yet have any sense of what was important, and what was not.

But around 7 all that information has coalesced into a general framework about how the world works and everything else becomes less important so the brain forgets it and starts collecting new information based on the framework that was formed.
Answer based on personal experience.

I think it depends on how intense those memories are?
They could be intensely bad, intensely happy or may be something unique.

I can clearly date my definitely earliest memory. I was born on 21 Nov 1958 and Goa was liberated by India on 19 Dec 1961. So I was about 3 years and 1 month at that time. On that day we all raised a flag of India on our houses. I was at my maternal uncle's place and remember they raising it on a long bamboo staff. When I came home I saw a flag on my house put on top of the house with small stick. I think there were some older memories about toys but they can not be dated.

My daughter named Uma Damle remembers the U on her 2nd birthday cake. That's all she remembers about it because it was first function with guests in her memory.

Typically, it depends on the level of emotion attached to the memory. Because most people don't develop a mature grasp on time until they go through puberty, memories prior to puberty are skewed or hazy.

However, that doesn't mean you can't have memories back to very, very young. My earliest memory, I learned as a adult, was from when I was just under two. It was a really frightening experience with my father and, due to the strength of the emotion attached, I still remember feeling afraid, what I was thinking, and what, specifically, was scaring me.

One of my kids has told me she remembers sitting in a high chair while I fed her, seeing something on the wall that scared her. From her description of what the room looked like and the fact that she was in a high chair rather than a booster seat, I know she was less than two.

Dr. i'm not quite sure what you mean by retaining. But over the time I have been digging into my own pathology, I have come to the believe that memories exist in different sorts. Among them manifest memories one can recall and unconscious memories or latent memories one cannot (actively) recall, or not recall at all. There is probably also the kind of memory that has been retained in our brain for sometime and maybe is of the second kind, but maybe has been forgotten. I am not sure about the question if we are actually able to really forget things, or that information we once have stored just becomes latent or dormant. Or, what forgotten actually means.

This opinion is based on the general assumption op psychologists that some personality disorders are basically formed in early childhood, before the age most people assume the memory actually becomes active and stuff can be stored until eternity.

However a personality disorder is there to stay too if not treated and will usually only grow over time. So the child will have to have memories of some kind that at least have to be stuck in the brain long enough to be reinforced before they fade. This led me to the conclusion that memories already are being formed and the brain is already being trained to memorize things at a very early age, maybe even prenatally. They might not be retained very long at start yet, but they are definitely there already.
I have memories from about 3 onward-  and about the same number of memories per year until five or so.  It seems to differ individually, but if we correlate memories and certain cogntive levels, it appears that when a child starts the shift from preoperational to concrete operations reasoning, newer memories overlay earlier ones in such a manner the earlier ones are no longer retrievable. 

It wouldn't surprise me if the same thing doesn't happen as the child moves from concrete to formal operations (solid abstract abilities) although the child is able to remember older memories better due to that same abstract reasoning providing experience.

Jean Piaget

Jean Piaget | Cognitive Theory | Simply Psychology

On average around 5, that's when most people start retaining memories, some a bit earlier others a bit later. Remarkable facts in a young child's life may help date the early memories, a loss, a radical change in residence, the birth of a sibling. I can distinctly remember in some detail the afternoon my mother came from hospital with my younger brother, I can even remember his red face when she bended to show us the baby, the mid-afternoon snacks we were having and how we ran from the table leaving the food behind when we heard the car. I was 3. But before 6, 7, I have only punctual memories like that one.

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