Learning a language is easiest at a young age during a window that researchers call the “sensitive period.” As people get older, language learning becomes much more difficult. This graph shows that young brains are especially responsive to learning language. The “sensitive period” for learning native language sounds is the first year of life. During this time, the infant brain becomes specialized to hear the subtle differences between the sounds of their native language. In this module, we focus on what happens next – speech production. Babies make sounds right from birth. By the time they are 3 to 4 years old, they speak in long and complex sentences. What are the different stages of speech development from birth up to about 3 to 4 years of age? On the graph, you will notice that this is the period of fastest language learning.