Final answer:
Judith's assumption that her brother would like a toy horse because she does is an example of egocentrism, a concept from Piaget's cognitive development theory indicating an inability to understand others' perspectives.
Step-by-step explanation:
Egocentrism refers to the inability to take the perspective of others and the belief that everyone sees, thinks, and feels the same way as oneself. In this case, Judith assumes that her brother would have the same preferences as herself, without considering his individual tastes and interests.
Judith's belief that her brother would enjoy a toy that she herself would enjoy while shopping for a gift is an example of egocentrism. Egocentrism is a cognitive characteristic where a child is unable to take the perspective of others, assuming that everyone sees, thinks, and feels the same way they do. The concept of egocentrism is prominent in Jean Piaget's theory of cognitive development, particularly during the preoperational stage, which typifies young children's thoughts.