Describes an experiment to see whether the words "front" and "back" introduce the concept of "front-back" or whether the concept preceded the words. Results show that (1) a complex disjunctive concept of "front-back" orientation precedes any knowledge of the words; (2) linguistically, "back" is comprehended before "front"; and (3) children at an intermediate lexical stage interpret "front" as "back." (EKN)