Causal loop diagrams are designed to show the ongoing  dynamic interaction between elements in a system.

The most simple is the chicken and egg  system.

The arrows denote causal connections, while the S at the end of the arrow indicates that  when the causal variable increases the dependent variable moves in the Same direction: chickens  increase,  eggs increase. Likewise, if chickens decline,  so do eggs.

This dynamic between chickens and eggs generates a pattern of “behaviour over time.”

In this case, both chickens and eggs are increasing. In this case it is exponential growth because it is no balancing loop to bring the chicken population back under control.

One such balancing loop is where chickens cross the road.

In this part of the system, as the number of chickens increases so does the number of road crossings. However, as road crossings increase, the number of chickens declines. This is demonstrated by the O ( for  Opposite) at the end of the causal arrow. This is the balancing work because the dynamic is that the chickens and road crossings come into some form of equilibrium or balance.  The behaviour of the time for this is:

In this situation, the number of road crossings  go up until the chicken population is made up entirely of chickens who do not cross the road.