At around 11 or 12 weeks, your baby will enter yet another new world as he undergoes the third major developmental leap since his birth. You may recall that one of the significant physical developments that occurred at 8 weeks was your baby's ability to swipe and kick at objects with his arms and legs. These early flailing movements often looked comically puppetlike. At 12 weeks, this jerky action is about to change. Like Pinocchio, your baby is ready to change from a puppet into a real boy.

Of course, this transformation will not happen overnight, and when it does it will entail more than just physical movement, although that's usually what parents notice most. It will also affect your baby's ability to perceive with his other senses the way things change around him—such as a voice shifting from one register to another, the cat slinking across the floor, and the light in a room becoming dimmer as the sun dips behind the clouds. Your baby's world is becoming a more organized place as he discovers the constant, flowing changes around him.

Your baby's mental development is very important and significant. It affects not only your baby's mood, but also his health, his intelligence, his sleeping pattern, the three C’s (crying, clinginess, crankiness), and much more. Once you understand your baby’s mental development, you can help your baby in so many ways. If you would like to learn more about the mental development of your baby, order a copy of The Wonder Weeks, which is based on international research.