Hungry rats were given sequences of free and forced trials in 2 alleys, 1 containing constant food reward and the other containing varied amount or varied delay of food reward. Choice behavior indicated that the net incentive value of varied reward is neither the average of the rewards nor the average of the incentives as independently estimated. The average of these 2 averages provides a tentative rule of thumb consistent with delay-amount choices. (PsycINFO Database Record (c) 2016 APA, all rights reserved)