This research area studies the development process of language components or levels, mainly during the first stages of development.The focus is on normal development and language alterations.On the other hand, the process for acquiring second languages is also studied.The studies focus on linguistic transfer processes and on the cognitive aspects involved in the language teaching-learning.The methodology used in this research area is experimental (training studies) and observational (speech sample collections and analyses with the CHILDES system), as well as analyses of the data obtained from MacArthur-Housecoats CDI questionnaires adapted to Catalan.