Buy the unit you'd eat

The bowl works at the sofa. This chapter works at the shop, and it's the version of the method that needs no fifteen seconds at all, because the partition comes ready-made.

The small bags. A multipack of thirty-gram bags is the same crisps in units of a handful. Open one, eat it, done. The bag is the unit, and the unit is a few, and unit bias is on your side for the first time since sharing bags arrived. Zlatevska's curve says the difference between a small bag and a large one is the steepest part of the effect, and you're now on the right side of it.

Buy the partition. Sweets in small bags rather than a big one. Nuts in the little pots rather than the tub. Anything that comes pre-divided into the amount you'd actually want. You'll pay a little more per gram, and you'll eat a great deal less per evening, and the second saving is larger than the first cost.

Vary it. Cheema and Soman found that partitions lose their power as people get used to them, and keep it when they change. A small bag one night, a bowl from the big one the next, a different bowl the night after. Not for variety's sake, but because a partition you've stopped noticing has stopped partitioning.

The sharing bag as an occasion. You don't have to stop buying them. Buy them when there are four people to share with, and put them out in a bowl for the four people, and they'll do what sharing bags were named for. What you stop doing is buying one for a Tuesday on your own.

Don't buy in bulk. The economy of the big bag is only an economy if the big bag lasts as long as five small ones would. Chapter 18's arithmetic says it lasts one evening. Buy the size you'd eat, and the price per gram stops mattering, because the grams are the ones you wanted.

Leave the shelf's unit on the shelf. The shop has decided what a normal amount of crisps is, and it decided in its own interest. Walking past the sharing bag to the multipack is the whole of this chapter, and it takes as long as reading this sentence.