Regulatory complexity. The influence of the interaction between each pair of regulators (i.e. the cross-term β12 in the case of two regulators) is plotted against the influence of each individual regulator (i.e. β1 and β2 in the case of two regulators). In order to compare these values independently of the expression intensities of the particular module and transcription factors, we have plotted the T-statistics of the β's rather than their actual values. Statistically significant values are marked by dotted lines.