How old your child is when he or she gets a phone does not seem to have any effect on their development. In a new study published in the journal Child Development, researchers at Stanford followed a group of more than 250 children for five years. Over those five years, most of the children received their first cell phone. The average age at which children received their first phones was just over 11 and a half years old. Families generally chose an age when the parents felt it was best for the child. The researchers found that based on a number of different measures, the age at which children get their first phones has little, if any, effect on outcomes like grades, sleep, depression and well-being.