Fig. 2. Overview of signed null models.

A small toy network that contains two groups of nodes (even in yellow and odd in gray) is shown in the middle. The network is designed to be strongly balanced with positive edges only between members of the same group and negative edges only between members of different groups. We consider four null models: (i) rewire, disrupts the topology and signed node degrees; (ii) sign shuffle, preserves the topology, disrupts signed node degrees; (iii) signed rewire, preserves signed node degrees, disrupts the topology; and (iv) STP, preserves both the topology and signed node degrees. Positive edges are shown in blue, while negatives are in red. Thicker lines indicate edges that are different from the original network.