Individuals with Fragile X Syndrome show differences in how they understand and learn language from infancy. They frequently have lifelong delays in speech and language as well. In addition, they experience other auditory symptoms, including being very sensitive to certain sounds as well as being more sensitive than others to loud sounds. The underlying brain activity for sound perception and speech learning in Fragile X is not well understood, especially in the infant and toddler years. This study uses behavioral assessment of speech and language abilities, neuroimaging, and hearing tests to understand how speech and hearing are different in children with Fragile X Syndrome.