This diagram says that kid’s knowledge of nutrition affects parent’s knowledge of nutrition. This happens over a longer time frame as kid’s grow up to become parent’s themselves. Equally, parent’s knowledge of nutrition affects kids’ knowledge as parent’s pass their know-how on to their children. So, if kid’s knowledge increases, parent’s knowledge increases and vice versa. Once around the loop and we have reinforced the original behaviour we started with.

These reinforcing loops are the sources of huge growth and decline. Indeed, for the mathematicians, the pattern is exponential. The behaviour I have just described is virtuous but equally if we start with decreasing knowledge and follow the loop round the behaviour is vicious. Of course, we rarely see a single loop operating in isolation. Systems are all made of many loops like this.

Just as we have two types of relationship we have two types of feedback loop. The other type is balancing. An example is shown below.