How could one possibly come up with an idea of vision-distorting glasses?

In one such study, Schultz et al. asked children 3 to 5 years of age to perform a number of tasks. Some were quite easy, whereas others were designed so that mistakes would be made. For example, children were asked to point a shiny penny as opposed to a dull penny, or to observe another child doing such pointing. On half the trials children wore a pair of glasses that distorted their vision and caused them to pick the dull penny. Children as young as 3 were able do judge thet they were wearing the distorting glasses, and did mean to pick the shiny penny when no glasses were worn.

–Schult, Carolyn A. (2002) Children’s Understanding of the Distinction between Intentions and Desires. Child Development 73:1727-1747.

In the same article, you may read about the difference in perception of intentions and desires by children and adults. That children can’t tell intention from desire. It’s like an inability to learn a new language after reaching a certain age.

It’s like losing an ability of abductive reasoning.