Harry Triandis is best known for his foundational work in cross-cultural psychology, particularly his theory on individualism and collectivism. He developed the concept of 'cultural syndromes' to describe patterns of shared attitudes, beliefs, and norms that characterize cultural groups. His research provided a comprehensive framework for understanding how cultural differences in values, particularly at the individualistic-collectivistic level, shape a wide range of psychological phenomena, from social cognition and motivation to communication styles and organizational behavior.

Subjective culture, a core concept in Triandis's work, refers to a cultural group's characteristic way of perceiving its social environment. It encompasses the shared beliefs, norms, roles, and values that are learned and transmitted among members of a society. Triandis argued that to understand human behavior, one must understand the subjective culture in which it occurs, as it provides the 'lens' through which individuals interpret and react to the world. He meticulously developed methods to measure and analyze these shared psychological characteristics.

Harry Triandis spent the vast majority of his distinguished academic career at the University of Illinois at Urbana-Champaign, where he was a professor of psychology. He served as the head of the Department of Psychology and held the esteemed position of Professor Emeritus after his retirement. He was also a key figure in the university's interdisciplinary initiatives, helping to establish it as a world-leading center for research in cross-cultural and cultural psychology.

According to Harry Triandis, individualism is a cultural pattern in which people prioritize personal goals over group goals, value independence and self-reliance, and define their identity through personal attributes. In contrast, collectivism is a pattern where group goals and harmony are prioritized, individuals value interdependence and loyalty, and identity is closely tied to group memberships. Triandis emphasized that these are not binary categories but rather spectrum-like cultural syndromes that can vary within and between nations.

Triandis defined a cultural syndrome as a 'pattern of shared attitudes, beliefs, categorizations, norms, role definitions, and values that is organized around a theme and is found in a given culture.' He identified several key syndromes, the most prominent being individualism and collectivism. Other examples include cultural tightness versus looseness (which refers to the strength of social norms and tolerance for deviance) and cultural complexity. These syndromes provide a valuable way to characterize and compare different cultures at a psychological level.

Harry Triandis authored and edited many influential books and articles. His seminal book, 'The Analysis of Subjective Culture' (1972), was groundbreaking in its systematic empirical approach to studying culture. He later published 'Individualism & Collectivism' (1995), a highly influential work that remains a cornerstone in the field. He also co-edited the 'Handbook of Cross-Cultural Psychology,' a multi-volume set that has been essential for students and researchers in the discipline.

Harry Triandis is considered one of the founding figures of modern cross-cultural psychology. He provided rigorous methodological and theoretical frameworks that elevated the study of culture from a niche interest to a central aspect of psychological inquiry. His concepts of subjective culture and cultural syndromes, particularly his detailed treatment of individualism and collectivism, are fundamental to the field. His work has had a lasting impact on diverse areas, including social psychology, organizational behavior, and international business.