Psychologists have an excellent understanding of human behaviour. They have studied the brain, memory, learning, human development and the processes determining how people think, feel, behave and react. Psychologists apply their expertise using reliable and scientifically supported methods. Psychological therapies are widely used to treat individuals and families and can also be applied to groups and organisations. Psychologists assist people with everyday problems such as stress and relationship difficulties, and some specialise in treating people with a mental illness. They help people to develop the skills needed to function better and to prevent ongoing problems.