This complex interaction between meanings, objects, and behaviors, Blumer reiterated, is a uniquely human process because it requires behavioral responses based on the interpretation of symbols, rather than behavioral responses based on environmental stimuli. As social life is a "fluid and negotiated process," to understand each other, humans must intrinsically engage in symbolic interaction. Blumer criticized the contemporary social science of his day because instead of using symbolic interactionism they made false conclusions about humans by reducing human decisions to social pressures like social positions and roles. Blumer was more invested in psychical interactionism that holds that the meanings of symbols are not universal, but are rather subjective and are "attached" to the symbols and the receiver depending on how they choose to interpret them.