Almost all babies go from understanding no language to understanding and saying thousands of words in just a few years. Many parents have used language milestones for spoken and receptive language to assess their children’s development, as some of these milestones have been around since at least the 1930s1. Language milestones typically list ages and milestones that can be expected for infants and children who are learning spoken languages. For example, the milestone may be “making language-related babbling sounds” and the age range listed may be around 4 to 6 months of age. The purpose of those milestones is in part so parents will be aware if their infants are “on track” when learning to understand and say words. Since virtually every hearing baby in the world is in an environment where they hear language, there is normative data for when infants typically acquire certain language skills. There are often enormous differences in language abilities in young children based in large part on their early language environments.
The early literacy milestones that I describe here do not contain age ranges in part because written language environments in early childhood vary from regularly seeing and hearing words simultaneously during infancy frequently to not focusing on written words until the child is 5 or 6 years old. The purpose of these milestones is to help your very young child achieve early literacy skills. There are numerous guidelines to help you understand the process as well as specific tips designed to help your child achieve each milestone.
Just like other language milestones, environmental factors—like how much language the child sees and hears, the age at which the child begins learning written words, and how the caregivers interact with the child—are at work. So, very young children reach these milestones at dramatically different ages. And some children may reach a few of the milestones in a slightly different order.
1 Gesell, A. (1935). Cinemanalysis: A method of behavior study. Journal of Genetic Psychology, 47, 3-16.