When do we become aware of self?

I decided to watch the video entitled The Secret You. Sensations of the world like sounds, feelings etc. are something we all take for granted. We never realize how much we use them each and everyday and without them we all would disappear. The immense capabilities that goes on in our heads is miraculously changing with age. When we become aware of our self, we become aware of our surroundings. Our self changes with time, age, and experiences we face. In this video they did a test to figure out when we initially become self aware. They used two little children, one baby boy and the other, a little bit older girl, when the little boy had a sticker put on him he looked into the mirror and didn't even notice it, but when they out it on the girl, She noticed it right away. According to this test, between the ages of 18 and 24 months we become self aware.