Sixty healthy subjects with previous psychedelic experience underwent a double-blind, randomized, placebo-controlled parallel-group study design to test the effects of psilocybin on divergent and convergent thinking (DT and CT, respectively) and the biological predictors of these changes in DT and CT. Biological predictors include changes in network connectivity between different resting-state networks and were measured using resting-state fMRI. DT and CT were measured using cognitive tasks. Subjects were given either a placebo or psilocybin, and effects were measured acutely and seven days after administration. Psilocybin acutely increased ratings of spontaneous creative insights, while decreasing (deliberate) task-based creativity. These changes were predicted by within and between-network connectivity of the DMN.