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The encode–decode model of communication
The encode–decode model treats communication as sending a message: one person puts meaning into a signal, the signal travels through a channel, and another person recovers the meaning from it.
The basic idea
You have an idea you want to share. You encode it into a signal such as spoken words, writing or a gesture. The signal travels along a channel (air, a phone line, a text message). The listener decodes the signal and, if all goes well, arrives at the idea you intended. This is also called the code model or the transmission model. It grew out of Claude Shannon’s engineering work on telephone and telegraph systems (Shannon, 1948; Shannon & Weaver, 1949), and later writers adapted it to human communication.
The parts of the model
| Part | What it does | In everyday talk |
|---|---|---|
| Source (sender) | Has a message or intention | The speaker decides to ask for the salt |
| Encoder (transmitter) | Turns the message into a signal | Choosing words, planning sounds, moving the articulators |
| Channel | Carries the signal | Air between two people, a phone line, a text thread |
| Noise | Anything that distorts the signal | Restaurant clatter, a poor connection, hearing loss, distraction |
| Decoder (receiver) | Turns the signal back into a message | Hearing, perceiving and understanding the words |
| Destination | Ends up with the message | The listener passes the salt |
Later versions added feedback, so the receiver can signal back that the message arrived (Schramm, 1954), and Roman Jakobson (1960) described six factors in any communicative act: addresser, addressee, message, context, code and contact.
A worked example
Mei says “Could you pass the salt?” to Daniel across a noisy restaurant table.
- Encoding: Mei chooses the words, the polite question form and a rising tune, then produces the sounds.
- Channel: the sound travels through the air.
- Noise: background music masks the end of the sentence.
- Decoding: Daniel catches “could you pass the sal…” and works out the rest from the situation.
The message arrived even though part of the signal was lost, because listeners fill gaps using what is predictable. That predictability is called redundancy, and it is explored in entropy and redundancy.
Why the model is useful in speech and language therapy
The model gives clinicians a quick way to ask where a breakdown might be happening.
| Where the difficulty sits | Examples |
|---|---|
| Encoding (formulating the message) | Finding words after a stroke, organising sentences |
| Transmitting (producing the signal) | Speech sound disorders, dysarthria, voice problems, stuttering |
| Channel and noise | Poor acoustics, background noise, a bad phone line |
| Receiving (hearing and perceiving) | Hearing loss, difficulty processing speech in noise |
| Decoding (understanding) | Language comprehension difficulties, limited vocabulary |
Strengths and limits
The model is simple, easy to teach and good at describing signals, noise and errors. It is less good at describing how people work out what others mean, because meaning is not simply packed into words and unpacked again. We look at those limits in problems with the encode–decode model.
Key idea. Use the code model to locate where a signal is being lost or distorted, and other models to understand how listeners interpret it.
Sources and further reading
- Shannon, C. E. (1948). A mathematical theory of communication. Bell System Technical Journal, 27, 379–423 and 623–656.
- Shannon, C. E., & Weaver, W. (1949). The Mathematical Theory of Communication. University of Illinois Press.
- Schramm, W. (1954). How communication works. In W. Schramm (Ed.), The Process and Effects of Mass Communication. University of Illinois Press.
- Jakobson, R. (1960). Closing statement: Linguistics and poetics. In T. A. Sebeok (Ed.), Style in Language. MIT Press.