Equilibration

     Piaget’s notion of "equilibration" in the process of cognitive development might be helpful to explain the critical period phenomenon. For starters, the critical period coincides with the cognitive development during childhood and ends with the final stage of cognitive development. This suggests some connection between the two. Piaget described children’s cognitive development as a process of equilibration. During this process, the child swings from stages of certainty to stages of uncertainty. For example, during a stage of certainty, or "equilibrium", the child feels that he understands his world well and either does not care about, or does not notice his lack of understanding. In other stages however, known as "disequilibrium", the child realizes that he does not fully understand something and becomes highly motivated to figure it out. At these points, the child will be highly centered on what he is trying to learn and will put everything he has into it. It is during these stages of "disequilibrium" that children progress to their next level of cognitive development. In other words, their new understanding of their world culminates in a new level of thought. According to Piaget, a new level of thought naturally results in a new level of language ability, because, language naturally follows thought. Once a child has new thoughts to express, he will search around for the language he needs to express those thoughts. In this way, "natural" language learning only happens immediately following cognitive development. Because adults have completed this process of cognitive development and are permanently in a state "equilibrium", they cannot have "natural" language learning. They already have a language with which to express their thoughts, so they feel no sense of desperation to learn any more language.