For as long as I can remember, I've been fascinated by change. How does an infant turn into a toddler, and then a preschooler, a child, an adolescent, an adult, and, eventually, a senior? What leads to changes in people's character, their intellect, their relationships with other people? What, if anything, unites evolutionary processes, regardless of whether they involve the evolution of species, the evolution of businesses, the evolution of national policies, or the evolution of a person's thinking about a specific topic?

This fascination with change led me to study the development of learning and problem-solving during childhood. Within the human lifetime, many of the greatest changes are seen from birth through adolescence; indeed, childhood can be defined as the period of life in which positive change is most dramatic.

Most of my research on learning and problem-solving during childhood has focused on the development of mathematical thinking. This interest began in childhood, when I became intrigued by the statistics on the backs of baseball cards: batting averages, hits, home runs, win-loss percentages, earned run averages, and so on. I spent innumerable hours engrossed in identifying from these statistics the best player at each position and which teams were most likely to win the World Series.

A variety of factors led to my pursuing this early interest in my research. When I began to do research, Piaget's theory, which was built in large part from observations of mathematical and scientific thinking, was the dominant approach to cognitive development. My early research was intended to show that Piaget had underestimated children's capacity for problem-solving and learning in these areas. Although the results of my early research supported this hypothesis, observing how tenaciously young children clung to their misconceptions about scientific and mathematical concepts led me to an enduring appreciation for Piaget's genius in designing revealing tasks, where answers and explanations on a single trial could lead to insights about children's thinking.

My appreciation for this aspect of Piaget's genius led to the discovery that I consider to be my most fundamental – fundamental in the sense that it provided the foundation for numerous subsequent discoveries.