With a little extra effort and some whiteout, he managed to decorate his friend to look very much like a pair of boots. This was all entirely humane. The end-product is depicted at the right. Even the youngest children claimed that the boots were still a rottweiler. This contrasts sharply with the claim that young children rely entirely on perceptual, or characteristic, features for categorization.
Children seem to start out as essentialists.
Ontological kinds are something like essences. Don't undergo a dramatic representational change as we get older. Are initially learned through identification of characteristic properties, but these are quickly over-shadowed by theories based on ontological kinds. Therefore Vygotsky is wrong. Prototype theory is inadequate.