Network motif analysis of node triplets reveal detailed interactions patterns in directed networks.

<p>(a) The thirteen possible motifs composed of three nodes in a directed network. (b) The fractions of each motif type in each of the six networks. Motifs accounting for fewer than 10% of the motifs are not shown. Friendship, Mail, and Shop each show one dominant motif, consistent with the high or low reciprocity found in the networks. (c) A closer look at the (normalized) Z-score triad census of Private Messaging, Party Invitation, and Trade networks where no dominant motif is evident, we used the Z-score method is employed to determine significantly over- and underrepresented triangular motifs. Overrepresented motifs (with ) are indeed closed triangles, consistent with the relatively high clustering tendencies in these networks.