To understand population change, it is not sufficient to know what life choices individuals and families make. We need to understand how choices are made. Critical choices in life, such as the choice to marry, to have a child, to migrate, to retire or to end the life course, are outcomes of cognitive processes. The processes involve substantial risk and uncertainty. They consist of stages and each stage takes time. Life choices have far-reaching consequences. Because of them, people’s lives and biographies are diverse, and population change is colourful but complex.