 Methodological innovation: the ‘violation-of-expectancy’ looking time. The work we discuss depended on solving a knotty methodological problem: how to discover what is going on in the minds of preverbal infants and very young children? Though infants cannot report on what they are perceiving or thinking, one can make inferences from their reactions to objects and events. Long before they utter their first words, they suck, grasp, creep, crawl, and—most importantly—they look. Since infants, like adults and other animals, look longer at an unexpected stimulus, where they look and for how long they look can reveal a good deal about their expectations about the world. While measures of grasping, crawling, and sucking have all been successfully used to reveal some of what is going on in the baby’s mind, the measure that has been used most extensively is the violation-of-expectancy looking time (sometimes called preferential looking time). Experiments using this measure tend to have a similar structure: during an initial phase, the child is presented with display \(X\), over and over, until the child’s interest wanes and looking time drops down to some criterion (the habituation phase). In the test phase, the child is presented with two displays: \(Y\) and \(Z\). If the child reliably looks longer at \(Y\) than at \(Z\), this provides evidence that \(Z\) is as expected, but that \(Y\) is unexpected.