Hi, my son is 20 months old. He is always interested in playing. He rarely concentrate when we speak to him when he is playing. He is not bothered about who is with him. He is friendly with everyone even when he meets them for the first time. He can stay with them even without parents. I feel he is not understanding who is what to him. I think he is not recognising us. But when he is sleepy, he needs Mom. Worried if he is normal.