Strategic Modelling and Business Dynamics: A Feedback Systems Approach

2.3. Structure and Behaviour Through Time - Feedback Loops and the Dynamics of a Slow-to-respond Shower

Causal loop diagrams are a stepping-stone to interpreting and communicating dynamics or performance through time. The best way to appreciate this point is to see a worked example. Here I present a hot water shower like the one at home or in a hotel room. In this example, we start from dynamics of interest and then construct a causal loop diagram that is capable of explaining the dynamics. Our analysis begins with a time chart as shown in Figure 2.7. On the vertical axis is the water temperature at the shower head and on the horizontal axis is time in seconds. Imagine it is a hot summer's day and you want to take a nice cool shower at 25°C. When you step into the cubicle the shower is already running but the water temperature is much too cold. The time chart shows three alternative time paths or trajectories for the water temperature labelled 'ideal', 'common sense', and 'most likely'. The ideal outcome is that you quickly adjust the tap setting by just the right amount and the water temperature immediately rises to the desired 25°C after which it remains rock steady. You are comfortably cool. Common sense says this ideal can't happen because, like most showers, this one is slow to respond. There is a time delay of a few seconds between adjusting the tap and a change in the water temperature. To begin with, the common-sense trajectory is flat and the water temperature remains ...