As humans we have the great advantage of being able to learn about the world from what other people tell us. In this way we can benefit from the knowledge and expertise of others rather than having to learn everything from our own direct experience. This learning mechanism is particularly significant for children’s knowledge acquisition, especially when it comes to learning about facts or events that the child cannot discover for herself (Harris, 2012). Testimony-defined in this sub-field as intentionally communicated verbal information-can shape the child’s learning through many guises. It is most clearly observed in instances of deliberate teaching by parents or teachers to which children are highly receptive (Csibra & Gergely, 2009), or when children themselves demand answers to their frequent questions. But it also takes place incidentally: through parents’ implicit guidance in their everyday conversations with their children (Callanan, Rigney, Nolan-Reyes, & Solis, 2012; Rogoff, 2003); through children’s overhearing of conversations held by others (Akhtar, Jipson, & Callanan, 2001; chapter 9); through exposure to written forms of testimony that constantly surround them (Robinson, Einav, & Fox, 2013); and more generally through the assimilation of subtle cues present in the language used by people in their community (chapter 2). In all these different ways testimony helps children make sense of their world.