Giving NPCs memories can go a long way to making a more realistic and enjoyable game world.
This is not a submission about creating NPCs, this is about presenting them. Not everyone walks around with a different accent, strange tic, or catchphrase, our memories are what make us different.
The size and number of knots in hair, tied around neck, or hanging from belt could signify family, importance, worship, guild affiliations. Being able to translate the meaning of the size and placement of knots can give you a a large understanding of who somebody is.
May be used in a more barbaric society. Where in cities peoples clothes and crests show who they are, barbarians have no need for this so use knots.