Why are we influenced by advertising? How much does nurture determine behaviour? What is imprinting? The 'Why Science Matters' series demonstrates how the science we learn at school is important in every aspect of our everyday lives. Using case studies and investigations, the series describes the development of science and technologies that can improve our lives - or lead to new scientific challenges and controversies. In 'Understanding Health & Behaviour', we look at how animals have clear patterns of behaviour, such as reacting to hunger and their response to meeting other animals. We find out how investigating behaviour can take place in the laboratory or a natural environment, and the role of both nature and nurture in animal and human development. And we learn how our diet, exercise, and drugs can affect the way we behave.