We have theories of development because observers of human behavior have been intrigued by what they saw childern and adults do. A 3-year-old predicts that a crayon box holds crayons; then, after it is opened to reveal candles, he asserts that he always believed that it held candles. A 5-year-old claims that spreading out a row of buttons increases the number of buttons. A school-age child uses a good strategy to successfully solve an addition problem but shortly later she uses a less reliable strategy on the same problem. An adolescent selects an identity without seriously exploring other possible identities. An adult reports a dream that seems to be a thinly disguised attempt to deal with childhood anxieties.