Integrated Information, a Complexity Measure for optimal partitions

Motivated by the possible applications that a better understanding of consciousness might bring, we follow Tononi’s idea and calculate analytically a complexity index for two systems of Ising spins with parallel update dynamics, the homogeneous and a modular infinite range models. Using the information geometry formulation of integrated information theory, we calculate the geometric integrated information index, ${\phi }_G(\mathrm{\Pi })$ for a fixed partition $\mathrm{\Pi }$ with $K$ components and $\mathrm{\Phi }=$max${}_{\mathrm{\Pi }}{\phi }_G(\mathrm{\Pi })$ for $K=2$ or $3$. For systems in the deep ferromagnetic phase, the optimal partition undergoes a transition such that the smallest (largest) component is above (resp. below) its critical temperature. The effects of partitioning are taken into account by introducing site dilution.