American structuralism was pioneered in the early 20th century by linguists such as Edward Sapir and Leonard Bloomfield. It is based on the idea that the structure of language can be understood through analyzing the relationships between linguistic units without reference to meaning. Bloomfield's approach known as American structuralism emphasized empirical observation and rejected mentalist explanations. It can be divided into two phases: Bloomfield's behaviorist approach and later distributionalism pioneered by Zellig Harris.