A diagram of the concept of metric distance versus topological distance as applied to schools of fish. In the Metric Distance Model (left), the focal fish (yellow) pays attention to all fish within the zone of repulsion (red), the zone of alignment (lighter red) and the larger zone of attraction (lightest red). In the Topological Distance Model (right), the focal fish only pays attention to the six or seven closest fish (green), regardless of their distance. Derived from Metric vs topological distance for animal aggregations.png with text removed.