Leidy Klotz from his book Subtract: The Untapped Science of Less:
In one study, recently published in Nature, we challenged participants to modify a sandwich-like structure made from Legos so that it was strong enough and high enough to hold a masonry brick above the head of a stormtrooper figurine. Each participant received a structure consisting of parallel horizontal Lego panels connected by a vertical column that narrowed to only one block wide where it connected to the top panel. We asked participants to: “Improve this project so that it can hold a brick above the storm trooper’s head without collapsing.”
And we offered an incentive: “You will earn one dollar if you successfully complete this task. Each piece you add costs ten cents.”
The best solution is to remove the single block forming the thin part of the column. The top panel can then be attached to the larger section of the column, which stabilizes the structure and still leaves enough clearance to avoid the storm trooper getting squashed by the masonry brick.
Subtracting one block was the fastest way to solve the problem. Plus, only subtracting allowed participants to earn the full dollar. And yet participants were still more likely to add than subtract. This was evidence that people add to their detriment—at least when trying to modify a Lego structure so that it can hold a brick safely above the head of a stormtrooper.
To try to override the greater accessibility of adding, we also gave some participants subtle reminders, or cues, that subtraction was an option. If those who received the cue subtracted more often, then that would indicate that those who didn’t receive the cue were overlooking subtraction.
The experimenter said to all participants, “You will earn one dollar if you successfully complete this task. Each piece that you add costs ten cents.” Participants randomly assigned to the cue condition heard one more instruction from the experimenter: “but removing pieces is free and costs nothing.”
In the no-cue group, 41 percent subtracted a block. In the cue group, 61 percent subtracted. Those who were cued took home an average of eighty-eight cents, 10 percent more than those who didn’t get the cue.
The simple and subtle eight-word cue showed people a profitable solution that they had otherwise been missing. It sure seemed like people who didn’t receive the cue were missing the subtractive option not by choice but because they couldn’t see it.