The costs of eating: a behavioral economic analysis of food refusal.

Three kids with food refusal ate lunch at a small table.

The team gave them different spoon sizes—tiny 0.3 g up to big 9 g.

If the child said no, the adult held the spoon still at the lips until one bite went in.

They counted how many bites were accepted each meal over the study period.

Smaller spoons acted like cheap coins—kids took almost every bite.

Big spoons were expensive—acceptance dropped in a smooth line.

When the team added gentle guidance at the smallest refused size, acceptance jumped for that size and for bigger spoons they had not practiced.

The demand curve stayed the same shape, just moved higher.

McMullen et al. (2017) used the same guidance-plus-hold trick at the dentist.

Their patient stopped fighting cleanings for three years, showing the prompt works across body parts.

Bordi et al. (1990) faded written checklists for adults with brain injury.

Both studies fade prompts after the first correct response, matching the spoon-size fade used here.

Pichardo et al. (2026) later showed moms can track feeding data as well as trained observers.

That means you can let parents run the spoon-volume protocol at home without losing accuracy.

You now have a built-in ruler: spoon size equals price.

Start with the smallest spoon the child already accepts, add gentle guidance, then move up the scale only after three clean swallows.

Parents can collect the data, so treatment continues at the dinner table instead of only at the clinic.