The explanation that first leapt into my mind (as someone who grew up poor and is now not-poor BTW) didn't seem to be considered. For some kids, snacks are a l

The explanation that first leapt into my mind (as someone who grew up poor and is now not-poor BTW) didn't seem to be considered. For some kids, snacks are a luxury. For others, they're an unremarkable part of the background. This is going to make a huge difference in people's responses, but not as a matter of hunger vs. satiety. There's a whole different part of the brain associated with status and self-image; I'll bet that's the part that lights up differently for the once-poor vs. never-poor. An fMRI should shed some good light on the matter.