The field of cognitive development has changed dramatically over the last three decades. The field used to be dominated by Piaget’s theory of cognitive development (Piaget, 1954), which conceptualised cognitive development as taking place within the head of the child, according to an internal programming of cognitive change based on states of “disequilibrium” between the child’s mental states and the external world. Children were assumed to think and reason in a different way during each of the 4 stages of cognitive development (0 - 2 years, 2 – 7 years, 7 – 13 years, adolescence and adulthood). It is now recognised that children think and reason in the same ways as adults from early in childhood. Children are less efficient reasoners than adults because they are more easily misled in their logic by interfering variables such as contextual variables, and because they are worse at inhibiting irrelevant information. Logical skills improve as children get better at identifying irrelevant contextual variables and at inhibiting competing information; however note that adults also reason irrationally in situations when their contextual understanding is limited. The major developmental change during the primary years is the development of self-regulatory skills. The ability to self-regulate one’s thoughts and actions is conceptualized as “metacognition” and “executive function”, both discussed below. Hence cognitive development is no longer thought of in terms of “age bands”, with