It's started. DS is 18 months and has recently said the word "mine" a few times when referring to toys or books, but never in a cranky way. Until today. We had been swimming and were leaving the pool, I asked him if he could give me his cup so I could pack it in the bag before we walked to the car. His response - "no no no. Cup MINE!" and clutched it to his chest.
So, how long do they do this for? When do they get over it? Any handy hints for explaining sharing and taking turns to an 18 month old?