In a well-known experiment (Gopnik and Astington, 1998), children aged three to six were shown an oblong bag of M&Ms and then asked what they thought was inside. They all answered "M&Ms," and presumably were all disappointed to see that there was only a pencil in the bag.

When asked a little later what response a friend would give upon seeing the bag of M&Ms, most children responded, as if it were perfectly obvious, with: "A pencil." Even more remarkably, when children were asked to recall what they thought was in the M&Ms bag when they first saw it, almost all answered: "A pencil.".

What this test shows is that young children cannot imagine that their friend has a different perspective than they do, nor that their own perspective might be changed.