One of the big issues of human cognitive development is language acquisition process, and constructive approaches have been attacking the issue to understand this process by building vocal robots. This talk gives a survey on these approaches. First, cognitive developmental robotics is briefly introduced to show a general idea of these approaches. Then, learning of vowel vocalization by parrot-like teaching is shown as one of the model of the interaction between an infant and a caregiver. Next, caregiver's anticipation during the interaction process is analyzed, and as a result, it is shown how caregiver shapes the infant vowels. Finally, future issues are discussed towards language acquisition by cognitive developmental robotics.