Cycles and graph shape

Why a Tree of Influence is a directed graph, and what a cycle tells you.

Not a strict tree

Despite the name, a Tree of Influence is not a strict tree. One problem can influence many nodes, and many nodes can influence one outcome. Paths branch apart and come back together. In technical terms, it is a directed graph.

Its natural shape is a directed graph with no cycles: every path flows forward, from roots toward outcomes.

Cycles are signals

Sometimes two problems seem to feed each other: A makes B worse, and B makes A worse.

Do not draw a two-headed arrow, and do not invent a special notation. A cycle like this is a signal that a cause has not been found yet.

Self-reinforcing loops tend to dominate everything else on the board, precisely because they feed themselves. That makes the cycle one of the most important things to investigate. Ask the group:

What makes both of these worse? What is underneath them?

In this example, the group discovered that developers chose suboptimal solutions because there was too little automated test coverage. Without a safety net, nobody dared to step away from the status quo. The new problem goes on the board, and the cycle dissolves into a chain:

When a cycle survives

If a cycle survives several rounds of refinement and nobody can find a cause underneath it, leave it on the board as 2 separate arrows. No special notation is needed. The fact that it resisted decomposition is useful information in itself.