What are multiple cause diagrams?
Animated tutorial 9: what are multiple cause diagrams?
How to draw multiple cause diagrams
Drawing a diagram from scratch
Drawing a multiple cause diagram – technology and food supply in farming
The purpose of this type of diagram is to consider events, and states of things (i.e. states of things like low morale in the workforce, or poisoned water in the pond), and to explore the causal connections between them – for example, why a given event happened or why a certain class of events or states tends to occur. It is useful for finding out why something went wrong or keeps recurring. These diagrams have an important feature in that they identify feedback loops. Understanding unpredictable dynamics is often helped by unravelling the interaction between different feedback loops.
- A title describing the purpose of the diagram.
- Phrases describing events or states of things.
- Arrows (which may occasionally be labelled) signifying causality.
- The nodes of the diagram consist of phrases that relate to a state or an event (e.g. ‘flat battery’ or ‘battery goes flat’, respectively).
- Arrows indicate the causal connections between the phrases, and are read as ‘phrase at tail of arrow’ causes ‘phrase at head of arrow’, for example ‘leaving lights on’ causes ‘flat battery’.
- In general, arrows are not labelled. However, it is acceptable to do so if you wish to add information about the type of causal connection, e.g. ‘length of time lights are left on’ reduces ‘amount of charge in battery’ (to emphasise that an increase in one leads to a decrease in the other). Or ‘leaving lights on’ contributes to ‘flat battery’ (to emphasise that this is unlikely to be the only cause).
- Unlabelled arrows must be able to be read as ‘causes’, ‘effects’ or ‘contributes to’ (e.g. ‘length of time lights are left on’ affects ‘amount of charge in battery’).
- The chain of causal connections may be entirely sequential or it may include loops.
- In constructing such a diagram you normally begin at the state or event to be explained and work backwards. A diagram should include more than one such end factor only if contributory factors were related, and explaining both events is important.
- It is conventional not to put blobs around phrases, although if it improves clarity you can.
- It is not essential to indicate a system boundary on a multiple cause diagram. However, drawing a multiple cause diagram may help develop your ideas about where to draw a boundary.
- It helps in checking a draft to ensure that each individual relationship makes sense. If the meaning is not obvious, then often the cause is that you have omitted some intermediate nodes, and finding and inserting them solves the problem.
- Take care not to combine two factors into one, e.g. ‘battery is flat and car won’t start’. This can prevent you identifying differences in their causes or consequences, and therefore can prevent you from finding potential good points at which to intervene in the situation.
- This type of diagram does not distinguish between necessary and/or sufficient causes – if the distinction is important for your purpose you will need to annotate your diagram to indicate this.
- It is important to remember that this diagram type, while superficially resembling an influence diagram, is different in that the nodes of an influence diagram represent components of a situation, whereas the nodes of a multiple cause diagram represent events or states.