What we have learned

This special issue celebrates the fortieth anniversary of the Journal of Child Language by presenting reflections on the past and future of research on child language acquisition. In the spirit of this celebration, I review informally the major principles we have identified, the ideas we have rejected, and some of the crucial issues remaining to be explored. Beginning with the positive findings, we can sort the principles we have confirmed into four categories: learning principles, processing principles, neurolinguistic principles, and social interaction principles.