Do we remember everything?
Do you think that the human brain actually stores all occurrences in time? In other words, do you think that we have storage for every picture we see throughout our entire life and that perhaps we just lose direct access to it from interference or that we truly forget?
I'm sure that our brains don't remember everything.
Memory constantly forgets useless information (see: Forgetting).
Moreover, our brains remember practically no pictures. Our brains do remember concepts which related with parts of pictures.
That's why if you observed a lot of cars then it will be easier to you to remember picture with couple of cars on the picture.
If you never saw cars before - you'll have huge problems with remembering the picture with cars.
So: We truly forget information with the time.
But at the same time information is stored in the brain in redundant form, so if one concept is lost then other concept could represent the necessary knowledge. However if all related to the knowledge concepts will be cleaned up then the knowledge will be lost.
But system can learn this information again :-)
Also there is such effect of forgetting, when a concept still exists but it is hard to activate the concept, because many related relations (axons) were lost.
For instance, you remember that you should take your documents when you go out of home, but this concept ("Take the documents") is not activated when you going out of home.
Later, because of another stimulus (police officer on the street, for instance) you will remember that you had to take the documents ("Take the documents" concept will be activated).
A cause of forgetting here is a "lack of references with the concept".
The cause of the "lack of references" could be "forgetting process applied to references" or "not all required references to the concept are created".
1) We definitely don't remember everything. We remember something.
2) We constantly forget information.
3) There are two type of forgetting: "concept forgetting" and "relations forgetting".
4) Even if information is completely forgotten, AI system can learn the information again.