The theory behind why material reward makes you perform worse than usual is: while thinking on the problem, thoughts about the reward take up some expensive res

The theory behind why material reward makes you perform worse than usual is: while thinking on the problem, thoughts about the reward take up some expensive resources in the brain. Compared to intrinsic rewards, extrinsic ones are a novelty for the brain, so it can't help but build plans about some new possible "futures".