Halford et al.'s analysis of relational complexity provides a possible fram
ework for characterizing the symbolic functions of the prefrontal cortex. S
tudies of prefrontal patients have revealed that their performance is selec
tively impaired on tasks that require integration of two binary relations (
i.e., tasks that Halford et al.'s analysis would identify as three-dimensio
nal). Analyses of relational complexity show promise of helping to understa
nd the neural substrate of thinking.