At 15–18 months, there is a lot going on in the development of a child. Expect curiosity, strong bonds, new words, independent walking, minor hand gestures, and more at this age. Talking and listening, reading, moving, playing outside, practicing daily tasks, and interacting with others are all beneficial to growth. Your baby's brain grows significantly between the ages of 1 and 4. The amount it grows depends on how much your baby learns. So if you want her to be able to function properly when she starts school, it's important that she gets adequate rest and relaxation too. A study published in 2004 in the journal Developmental Psychology found that young children who spent more time learning new skills grew more brain cells than children who spent less time learning new things. It also found that girls developed more brain cells than boys, but that men grow more brain cells overall so gender doesn't matter as much as you might think. It's normal for your baby's development to surprise you. Remember that each child is an individual so don't compare your daughter to other mothers' babies. And if you have any concerns about her development, it's best to talk to her doctor rather than go by what you see on social media or in parenting magazines.