Middle childhood—conventionally going from about 6-11 years of age—is a crucial yet under-appreciated phase of human development. On the surface, middle childhood may appear like a slow-motion interlude between the spectacular transformations of infancy and early childhood and those of adolescence. At the beginning of this stage, emergent cognitive abilities enable children to handle more complex intellectual problem-solving and to better understand reciprocal social relationships than they could in early childhood. In reality, this life stage is anything but static: the transition from early to middle childhood heralds a global shift in cognition, motivation, and social behaviour, with profound and wide-ranging implications for the development of personality, sex differences, and even psychopathology.