"I don't remember eating that much"

The surprise at the bottom has a particular quality. It's not that you decided to eat the bag and regret it. It's that you don't remember eating it at all. The programme happened. The bag emptied. The two events don't seem connected.

That's not a failure of memory in the ordinary sense. It's what the screen does, and the research on it points at something you can use.

Suzanne Higgs, in 2002, ran two experiments in which women were asked, before eating, to think for five minutes about what they'd had for lunch. Those who'd been reminded of lunch ate less than those who'd spent the five minutes thinking about whatever they liked. In the second experiment, being reminded of today's lunch reduced intake, and being reminded of yesterday's lunch didn't. Their ratings of hunger and fullness were the same across conditions. What changed how much they ate wasn't their stomach. It was whether recent eating was in mind.

Robinson's review picked up the same thread. Enhancing people's memory of what they'd eaten reduced how much they ate later, by a moderate margin, though the effect may depend on how prone people are to eating without restraint. And the distraction finding from chapter 7 fits alongside it. Distracted eating raised later intake more than immediate intake, and the likely reason is that distracted eating doesn't get remembered, so it doesn't count, so the next meal happens as if it hadn't been.

That's the run. Eaten with a screen on, from a bag you can't see into, it leaves almost no memory, and food that isn't remembered doesn't do the one thing eating is supposed to do to appetite, which is register. You reach the bottom and don't remember the middle because there was nothing to remember. Your attention was on the programme for the whole of it, and the crisps went in without leaving a trace.

The practical answer is chapter 22. Two minutes of eating the snack while looking at it, before the screen goes on, is two minutes of eating that gets remembered, and Higgs's finding is that remembered eating is eating that counts. You'll have had your crisps, you'll know you've had them, and the next thing you eat will be eaten by a person who remembers.