The IB Psychology course looks at behaviour through three different approaches: biological, cognitive and sociocultural.  In modern psychology, it is understood that these three approaches interact rather than compete to explain behaviour.

This chapter looks at biological explanations of behaviour.  There are two key areas of study in this unit: the brain and behaviour, and genetics.  The HL extension to the unit is a study of animal models of behaviour.

In order to address the different topics, Major Depressive Disorder will be used as an example.

Each chapter is divided into smaller sections with quizzes to test for mastery of key vocabulary and "checking for understanding" questions with sample answers to check for broader conceptual understanding.

	Chapter 4.1 The brain and behaviour This chapter looks at the role of the brain, nervous system and endocrine system play in human behaviour.  The key topics of study are: How psychologists study the brain Localization of brain function Brain plasticity The role of neurotransmitters on behaviour The role of hormones on behaviour The role of pheromones on behaviour
	Chapter 4.2 Genetics and behaviour This chapter looks at the role of genetics on human behaviour - but also the interaction of genetics with the environment. The key topics of study are: The importance of the Human Genome Project How biologists investigate genetic theories of behaviour. Epigenetics and gene expression Genetic arguments for Major Depressive disorder Evolutionary arguments for behaviour Ethical considerations in genetic research
	HL Extension: Animal research HL students are asked to delve a bit deeper into the use of animals in research.  The key topics of study are Arguments for and against the use of animal models Research methods and the use of animals Ethical considerations in the use of animals The use of animals in genetic research