It has been 20 years since Bever's (1982) and Strauss and Stavy's (1982) books on U-shaped functions in human development were published. The three target articles in this issue describe several old and new U-shaped functions and new theoretical explanations for their existence. In this article, the authors will comment on two aspects of U-shaped functions that occur during the early months of life. First they will describe an inverted face effect that does not show a U-shaped function. Next they will discuss a very robust U-shaped function for the development of auditory localization that has yet to be explained. (Contains 1 figure.)