A methodological review of preference displacement research

White et al. (2021) read every displacement paper they could find. They located ten experiments that compared edible and tangible reinforcers head-to-head.

The team looked at how long items were available, how often they were paired, and how choices were scored. They wanted to see if edibles always beat tangibles.

No single pattern showed up. In some studies edibles won, in others tangibles stayed on top, and in others the order flipped halfway through.

The methods changed so much that the winner depended on the rules of the game, not the items themselves.

Sievers et al. (2020) seems to disagree. They gave kids longer turns with leisure items and saw edibles lose their top spot. White’s review says the same thing: longer access keeps tangibles alive.

Peck et al. (2024) also chimes in. They proved that if you let delay sneak into an effort task, discounting shoots up. White found the same sneaky problem in displacement work—tiny timing shifts change the whole outcome.

Cullinan et al. (2001) adds the why. Their computer task showed that rate, quality, delay, and effort each tug choice in its own way. White’s paper says we must control every tug or the hierarchy is junk.

Before you run your next paired-stimulus assessment, pick one rule and stick to it. Keep access times equal, keep sessions short, and test both edibles and tangibles every time. If you switch the rules halfway, your “favorite toy” might drop out for no real reason.