Dr. Slobin discusses how grammatical errors offer insights into how children use patterns in language development.
One of our main concerns as psycholinguists is figuring out the strategies that children use to discover the grammar of their languages. If you ask ordinary parents how their child learned to talk, they would probably say, "He just imitated. What's the problem?" Well, one problem is that if you listen to what children say, they often say things they couldn't have imitated. So a child might say something like "I breaked the glass" or "I falled down."
Adults don't say things like "breaked" and "falled," but children do. These errors are to us the best evidence that the child is doing something creative. The child is in fact working out the structure of the grammar. When you hear a child saying things like "breaked" and "falled," this means that the child has worked out the pattern for forming the past tense in English. English doesn't always follow that pattern, but the child has discovered a pattern.
All through the years of language learning, the child is struggling between two opposite problems. On the one hand, he or she wants to adapt language, a particular language, to the natural patterns of thought. On the other hand, the child has to accommodate to the particular grammar of that language. The result, of course, is our adult linguistic capabilities. But along the way, if you look carefully, you can see the interplay between these two factors.
Language is perhaps the most complex cognitive product we have. It's something that all human beings acquire within the first few years of life, regardless of the circumstances in which they grow up, and to a great extent regardless even of their intelligence. Language reflects something about the basic nature of the human mind. The fact that language is universally so patterned, and that it universally follows such stages of development in its acquisition by children, raises deep questions about the organization of knowledge.