Isabelle Likes to Socialise

Recently, we noticed that our little girl has started to smile at us.  During the day, I attempted to play with her by coo-ing and talking to her, or touching her face.  When she saw me, she would give me a heart-melting smile.  She must be a happy baby, because she often smiled or let out a chuckle in her sleep.  From my memories, Ian did not smile at us this early as Isabelle (just over one month old).  Perhaps, girls do develop faster than boys?