A City Guide To Lingyuan for The final section of this chapter introduces what is broadly considered to reflect the discipline of health psychology and the final chapter of this book addresses careers in health psychology. What is health psychology? Psychology can be defined as the scientific study of mental and behavioural functioning. Studying mental processes through behaviour is limited, however, in that not all behaviour is observable for example, is thought not behaviour? and thus for many aspects of human behaviour we have to rely on self-report, the problems of which are described elsewhere. Psychology aims to describe, explain, predict and where possible intervene to control or modify behavioural and mental processes, from language, memory, attention and perception to emotions, social behaviour and health behaviour, to name just a few. The key to scientific methods employed by psychologists is the basic principle that the world may be known through observation empiricism. Empirical methods go beyond speculation, inference and reasoning to actual and systematic analysis of data. Scientific research starts with a theory, which can be defined as a general set of assumptions about how things operate in the world. A City Guide To Lingyuan 2016.