Unlike cross-cultural psychology, which examines cultural differences in human psychology by treating culture as a variable within national and regional frameworks, cultural psychology posits that “culture belongs to people” and seeks to understand humans who transform together while mutually interacting with culture. In this approach, cultural psychology views culture as an “arrangement of signs” and interprets it as individual signs people use, asserting that the human mind evolves through continuous interaction with culture over time. Lev Vygotsky‘s “psychology of signs” is foundational for understanding cultural psychology.