Distances (i.e., D1, D2 or D3) need not be linear functions of responses. To reflect non-linear perceptions, PCI2 allows for powers of distances.
Power 1 (i.e., P1, the unsquared version) is currently recommended and is the default, but any power > 0 can be used.
Power 2 (i.e., P2, the squared version) gives more weight to larger differences between individuals. If the initial difference scores were 1, 2, and 3 (i.e., P1), squaring the differences (i.e., P2) results in distances of 1, 4, and 9.