Final answer:
A child who understands that their own thoughts are different from others has developed theory of mind (TOM), a cognitive ability usually forming between ages 3 to 5. This capability is part of social cognition and contrasts with egocentrism seen in younger children.
Step-by-step explanation:
A child that understands their thoughts are different from others exhibits theory of mind (TOM). This significant cognitive ability generally begins to develop between 3 and 5 years of age. TOM enables children to recognize that other people have their own thoughts, feelings, and beliefs, which may differ from their own. Through the acquisition of TOM, children can deduce that someone else may have false beliefs and they can understand social interactions better, including deception, persuasion, and empathy. This contrasts with egocentrism, which is characteristic of younger children who believe that others share their perspective. Egocentrism and assimilation are different aspects of cognitive development described by Piaget, while the the zone of proximal development refers to Vygotsky's concept involving the difference between what a learner can do without help and what they can do with it.