The world’s No. 1 baby app! Understand why your baby cries more at certain times, isn't himself or herself and... what you can do to help. During our research, which began in 1971 with Jane Goodall and the chimpanzees in Tanzania, we discovered that babies are more prone to cry and to be clingy or cranky from time to time. This behavior was shown to be related to a leap in the baby's mental development. More specifically, babies go through 10 mental leaps in the first 20 months of their life. A leap may be tough, but it's a positive thing: it gives your baby the opportunity to learn something new. Use The Wonder Weeks app to: - See when a leap starts and ends thanks to a personalized leap schedule - Be automatically notified when a leap is about to start - Learn to recognize the leaps based on the various signals your baby gives - Discover the new skills your baby develops with each leap - Stimulate your baby's new skills with 77 playtime games - Keep track of your baby's ...