Even if you try your very hardest, you probably can't remember anything from before your third birthday, and even then, the memories are probably made up of the odd still image and dark or blurry shapes rather than a "movie clip" type memory from when you got older. It's probably unlikely that the reason for this is just because it as a long time ago, you're no more likely to remember being two years old when you're 13 as when you're 30, but rather that the infant brain is simply not wired up properly at that age and can't form the memories in the first place. It's not that kids don't remember things (apart from that you have asked them to pick their clothes up off the floor at least five times), they remember who people are and to say please and thank you and all those kind of things. This is what is known as the "semantic" memory. What children lack is something called the "episodic" memory. This is the type that is responsible for remembering experiences. Whilst the semantic memory might help you identify what a cat is, episodic memory will take you back to a time you petted a specific cat. It is thought that the reason for this is that the hippocampus, the part of the brain responsible for tying together long and short term memories, doesn't really switch on until you reach about the age of three. It could be that, for the first couple of years of a person's life, their primary goal is to gather basic information about the world (using the semantic memory), and it's only after this groundwork has been laid that the brain can devote some of its energy to recording episodic memories. Your brain is simply too busy for frivolous stuff like remembering your first birthday party.