In the passage from the book, linear models only have one direction, from a speaker to a listener. For example, a teacher is giving instructions to a student, which the student would listen carefully and do certain reactions to respond, such as nodding, smiling to show that they have received the information from the teacher. Also, listeners will never send messages, they absorb only passively what the speakers have told them. Misunderstanding is easier to occur during linear models, because there were lack of connections between them.
While interactive models involve feed-backs from the listeners, but it still required a sender and a receiver. Refer to the previous example, after the teacher has given out instructions, the student would shares his/her own views or experiences based on the information that he/she has heard from the teacher. According to the text, all communications require people both send and receive messages. Therefore, interactive models still can not consider as communication.
