The consistent practice of healthy, protective hygiene behaviours and the appropriate use of existing or newly created infrastructure are core outcomes of any WASH programme. Social and behaviour change aims to understand the barriers and motivators for change and to enable individuals and communities to practise safer hygiene. Strategies to trigger and motivate change draw on a variety of factors and focus both on the individual and the predisposing and enabling factors (chapter  P ).
 
Hygiene behaviour change can be defined as an adoption or increase in hygiene behaviours (such as handwashing with soap or the safe handling of drinking water) and a decrease in risky behaviours for a defined target population. The ideal outcome of hygiene behaviour change is that all individuals in the target population consistently and habitually practice the intended behaviours and thereby protect themselves against communicable diseases. The way that a programme achieves this must respect the autonomy of the individual and engage them in the change process (chapter  E ).
 
The brain responds to stimuli from the environment and ultimately controls behaviour. Hence hygiene behaviour change recognises the importance of human psychology and of understanding how people’s minds work. This chapter provides an overview of the most relevant psychological motivators and barriers, the processes that influence people’s hygiene behaviours and briefly introduces the theories that inform them. B.1 outlines the key concepts of social and behaviour change, B.2 describes some of the key models and theories of change. B.3, B.4, B.5, B.6 and B.7 provide additional information about motivators and barriers and how these behavioural factors can be employed to achieve hygiene behaviour change. The final sub chapter B.8 presents an overview of existing behaviour change approaches.