The point is, if the reward not just occurs rarely but were actually-kinda-disappointing, the pigeon gets even crazier than it had been huge jackpots, somehow.

The point is, if the reward not just occurs rarely but were actually-kinda-disappointing, the pigeon gets even crazier than it had been huge jackpots, somehow. Discrepancy between perceived and mathematical expectation is a big factor in keeping us hooked. So techniques to exaggerate the former are used.