Despite major parallels, cognitive development in human children and non-human primates rapidly diverges in fundamental ways. Young chimpanzees ignore helpful information offered by others, but children are attentive and amenable. A notable index of children’s receptivity is their asking of questions. Recent evidence shows that two-year-olds ask a remarkable number of questions and that most of their questions are aimed not at getting attention, permission, or help, but at getting information. They ask about unfamiliar objects (“What’s that called?”), about locations (“Where are my scissors?), and ongoing activities (“What’s the little bird doing?”). At around 30 months, children also begin to ask for explanations (“Why is the cereal hot?” or “Why do cats like milk?”). This seminar explores the emergence of questions with two key issues in mind: First, participants are examining the impact of family environment. Families vary dramatically in the amount and type of language input they provide to children. It is likely that such variation has an impact on the number and type of questions that children ask. Second, participants are examining whether the answers that children receive, especially to their requests for explanation, affect their conception of knowledge and its acquisition. Depending on how their questions are received, children are likely to vary in their ideas about: (a) what it means to know something; (b) the distribution of knowledge across members of their social environment; (c) the availability and adequacy of explanations; and (d) their own ability to allay puzzlement and to build knowledge by asking questions.