The shop that moved the milk

Supermarkets put milk at the back. The reason is often given as a trick to make shoppers walk past everything else, and that is part of it, but the smaller part.

Milk needs refrigeration, refrigeration needs plant, and the plant sits at the back where the delivery bay is. Moving the chiller to the front would mean running pipework across the shop and delivering through the shop floor. The layout is a consequence of cold chains and loading docks before it is a consequence of psychology.

This matters because the two explanations predict different things. If the placement is purely a trick, a shop could reverse it tomorrow at no cost and would do so if customers demanded. If it is driven by refrigeration and deliveries, then it will persist even in a shop with no interest in making people walk, and it does: small convenience stores with a single chiller put it near the back door for the same reason.

The useful habit here is to look for the dull explanation before the clever one. Clever explanations are more satisfying and they travel further, which means the ones you encounter have been selected for being interesting rather than for being right. The dull explanation is usually about physical constraints, legacy decisions or the cost of changing something, and it is usually at least partly true.

This does not mean shops are innocent. The route between the door and the chiller is designed with great care, and that design is psychology all the way down. The point is narrower: the position of the milk is mostly plumbing, and what happens on the way to it is mostly not.