In 2 experiments we explored young preschoolers' knowledge of constraints on human action by presenting them with violations of different types of law and asking whether the violations required magic. In Experiment 1, children responded that physical violations required magic more than did social violations. In Experiment 2, violations were…

Interest in U-shaped development has itself undergone a U-shaped progression. Twenty-five years ago, interest in U-shaped development was high. This interest was evident at a 1978 conference in Tel Aviv on "U-shaped Behavioral Growth" that resulted in the publication of a book of the same title 4 years later (Strauss, 1982). The breadth…

When a behavior disappears and then resurfaces, developmental psychologists typically look more closely at the behavior to figure out what is different before and after--that is, they increase the grain with an eye toward discovering how the system that generates that behavior has changed. But what ought to count as a U-shaped phenomenon? How…

"Little by little, the child develops," wrote an undergraduate in a friend's cognitive development class, and so, for the most part, it is. But what explains the U's of cognitive development? Namy, Campbell, and Tomasello and Cashon and Cohen take a standard approach to understanding U-shaped curves: as the product of a mix of different cognitive…

The traditional view of development is stage-like progress toward increasing complexity of form. However, the literature cites many examples in which children do worse before they do better. A major challenge for developmental theory, therefore, is to explain both global progress and apparent regression. In this article, we situate U-shaped…

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…

As the articles in this issue attest, U-shaped curves in development have stimulated a wide spectrum of research across disparate task domains and age groups and have provoked a variety of ideas about their origins and theoretical significance. In the authors' view, the ubiquity of the general pattern suggests that U-shaped curves can arise from…

U-shaped developmental functions, and their N-shaped cousins, have intrigued developmental psychologists for decades because they provide a compelling demonstration that development does not always entail a monotonic increase across age in a single underlying ability. Instead, the causes of development are much more complex. Indeed,…

The development of the "inversion" effect in face processing was examined in infants 3 to 6 months of age by testing their integration of the internal and external features of upright and inverted faces using a variation of the "switch" visual habituation paradigm. When combined with previous findings showing that 7-month-olds use integrative…

The articles in this collection consider one very interesting puzzle of development: U-shaped developmental functions. At some point during development, an organism might exhibit what seems like a regression from its expected developmental trajectory and, according to continuity models of development, this is aberrant. In this special issue,…