We know from behavioral studies, for example, that 10-month old babies are able to compare small quantities: if they see a person putting one biscuit in a box and two biscuits in another, most of them approach the latter box. We can draw conclusions from behavioral patterns about the way children’s thinking and abilities develop. Behavioral studies are structured, simple games children play with one or two adults in the presence of their parents. The game is recorded on video so that we can analyse children’s actions later – for example what they chose, where they pointed, where and how long they looked for something, or if they already speak, how they responded to our questions.