It is shown that one can obtain information about higher order structural correlations if one analyses the conditions under which vibrations of a network can be decoupled, and compares them with the Raman and i.r. data. The method applied to amorphous As2S3and As2Se3gives the ordering of the basic structural elements‐AsX3pyramids. It resolves a controversy about the structure of these glasses and clarifies its relationship to the crystalline structure.