Oh the irony: Perceptual stability is important for action

I review experiments in which drinking a sugarless drink causes some participants who have low blood sugar from fasting to give lower slant estimates. Ironically, this only occurs to the extent that they believe that they have received sugar and that the sugar was meant to make the hill look shallower; those who received sugar showed no similar effect. These findings support the hypothesis that low blood sugar causes greater participant cooperation - which, in combination with other experimental details, can lead participants to make judgments that can either seem to support the effort hypothesis or contradict it. I also emphasize the importance of perceptual stability in the perception of spatial layout.