Shannon-Weaver (1947) modelled communication as a linear, one-way process concerned mainly with engineering fidelity. The major criticisms were: (1) it ignored the meaning of messages, and (2) it treated communication as unidirectional. Wilbur Schramm (1954), working with Osgood, addressed both gaps. He conceived encoding and decoding as simultaneous, reciprocal activities — both sender and receiver are continuously encoding and decoding at the same time. He added the critical concept of the field of experience (the psychological frame of reference that each party brings), and incorporated feedback as an essential loop. The model also included context and recognised that meaning is negotiated, not merely transmitted. This made it far more applicable to human (as opposed to machine) communication.