Introductory models & basic concepts: Shannon-Weaver

The Shannon-Weaver Model

Please note: The Shannon-Weaver model is typical of what are often referred to as transmission models of communication. For criticisms of such models, you should consult the section on criticisms of transmission models.

If you have looked through the examples of typical everyday forms of communication, you will have noticed that some of the examples refer to less immediate methods of communication than face-to-face interaction, e.g. using the radio, newspapers or the telephone. In these cases, technology is introduced.

When, for instance, the telephone is used, you speak, the phone turns the sound waves into electrical impulses and those electrical impulses are turned back into sound waves by the phone at the other end of the line.

Claude Shannon and Warren Weaver produced a general model of communication:

This is now known after them as the Shannon-Weaver Model. Although they were principally concerned with communication technology, their model has become one which is frequently introduced to students of human communication early in their study. However, despite the fact that it is frequently used early in the study of human communication, I think it's worth bearing in mind that information theory, or statistical communication theory was initially developed to separate noise from information-carrying signals. That involved breaking down an information system into sub-systems so as to evaluate the efficiency of various communication channels and codes. You might ask yourself how viable the transfer of Shannon's insights from information theory to human communication is likely to be. The concepts of information theory and cybernetics are essentially mathematical and are intended to be applied to technical problems under clearly defined conditions. After you've read this section, which, I think, is a reasonable attempt to loosely apply Shannon's ideas to human communication, ask yourself whether you feel enlightened.

The Shannon-Weaver Model (1947) proposes that all communication must include six elements:

These six elements are shown graphically in the model. As Shannon was researching in the field of information theory, his model was initially very technology-oriented. The model was produced in 1949, a year after Lasswell's and you will immediately see the similarity to the Lasswell Formula.

The emphasis here is very much on the transmission and reception of information. 'Information' is understood rather differently from the way you and I would normally use the term, as well. This model is often referred to as an 'information model' of communication. (But you don't need to worry about that if you're just starting.)

Apart from its obvious technological bias, a drawback from our point of view is the model's obvious linearity. It looks at communication as a one-way process. That is remedied by the addition of the feedback loop which you can see in the developed version of the model:


A further drawback with this kind of model is that the message is seen as relatively unproblematic. It's fine for discussing the transformation of 'information', which might be, say &Hui9%/?PLM, but, when we try to apply the model to communication, problems arise with the assumption that meanings are somehow contained within the message.

Shannon-Weaver: The Source


All human communication has some source (information source in Shannon's terminology), some person or group of persons with a given purpose, a reason for engaging in communication. You'll also find the terms transmitter and communicator used.
For a fuller discussion of 'source', see The Lasswell Formula

Shannon-Weaver: The Encoder


When you communicate, you have a particular purpose in mind:

and so on. You, as the source, have to express your purpose in the form of a message. That message has to be formulated in some kind of code. How do the source's purposes get translated into a code? This requires an encoder. The communication encoder is responsible for taking the ideas of the source and putting them in code, expressing the source's purpose in the form of a message.

It's fairly easy to think in terms of source and encoder when you are talking on the phone (transmitter in Shannon's terminology). You are the source of the message and the 'phone is the encoder which does the job of turning your sounds into electrical impulses. The distinction is not quite so obvious when you think of yourself communicating face-to-face.

In person-to-person communication, the encoding process is performed by the motor skills of the source - vocal mechanisms (lip and tongue movements, the vocal cords, the lungs, face muscles etc.), muscles in the hand and so on. Some people's encoding systems are not as efficient as others'. So, for example, a disabled person might not be able to control movement of their limbs and so find it difficult to encode the intended non-verbal messages or they may communicate unintended messages. A person who has suffered throat cancer may have had their vocal cords removed. They can encode their messages verbally using an artificial aid, but much of the non-verbal messages most of us send via pitch, intonation, volume and so on cannot be encoded.

Shannon was not particularly concerned with the communication of meanings. In fact, it is Wilbur Schramm's model of 1954 which places greater emphasis on the processes of encoding and decoding. The inclusion of the encoding and decoding processes is very helpful to us since it draws our attention to the possibility of a mismatch between the operation of the encoding and decoding devices, which can cause semantic noise to be set up. With good reason, the source of the message may wonder whether the picture in the receiver's head will bear any resemblance to what's in his/her own. Schramm went on to introduce the notion of a 'field of experience', which shows a much greater awareness of the subtleties involved in human-to-human communication, drawing our attention to the numerous shared socio-cultural factors which are necessary for successful communication to take place (see David Berlo's S-M-C-R model).

Shannon-Weaver: The Message


The message of course is what communication is all about. Whatever is communicated is the message. Denis McQuail (1975) in his book Communication writes that the simplest way of regarding human communication is 'to consider it as the sending from one person to another of meaningful messages'.

The Shannon-Weaver Model, in common with many others separates the message from other components of the process of communication. In reality, though, you can only reasonably examine the message within the context of all the other interlinked elements. Whenever we are in contact with other people we and they are involved in sending and receiving messages. The crucial question for Communication Studies is: to what extent does the message received correspond to the message transmitted? That's where all the other factors in the communication process come into play.

The Shannon-Weaver model and others like it tends to portray the message as a relatively uncomplicated matter. Note that this is not a criticism of Shannon since meanings were simply not his concern:

Frequently the messages have meaning, that is they refer to or are correlated according to some system with certain physical or conceptual entities. These considerations are irrelevant to the engineering problem.


This was particularly emphasized in Warren Weaver's introduction to Shannon's paper:

The word information, in this theory, is used in a special sense that must not be confused with its ordinary usage. In particular information must not be confused with meaning.
In fact, two messages, one of which is heavily loaded with meaning and the other of which is pure nonsense, can be exactly equivalent, from the present viewpoint, as regards information.

It may however be a criticism of the application of Shannon's model to the more general area of human-to-human communication. Meanings are assumed to be somehow contained within the signs used in the message and the receiver can, as it were, take them out again. Matters such as the social context in which the message is transmitted, the assumptions made by source and receiver, their past experiences and so on are simply disregarded. In this respect, models which incorporate such factors are probably more revealing of the complexity of the communication process. (See, for example, the sections on Berlo's SMCR model or Maletzke's model of mass communication)

Shannon-Weaver: The Channel


You tap on a membrane suspended above a steadily flowing jet of water. The air under the membrane causes slight deflections in the jet of water. A laser is aimed at a receiver. The jet of water flows through the laser beam, deflecting it from its target. Every time the water jet is deflected by the movement of the air, the laser beam hits its target. The laser receiver is connected to a computer which takes each 'hit' and turns it into a 1 and each miss and turns it into a 0. The computer sends these etc. etc......

You get the idea: the air waves, the jet of water and so on are all channels. The words channel and medium are often used interchangeably, if slightly inaccurately. The choice (a pretty stupid one above) of the appropriate channel is a vitally important choice in communication. It's obvious that you don't use the visual channel to communicate with the blind or the auditory channel with the deaf, but there are more subtle considerations to be taken into account as well. A colleague of mine was clearly much more responsive to visual communication than I. To elucidate his arguments he would inevitably grab a pencil and a piece of paper and sketch out complex diagrams of his arguments. Though they may have help him to clarify his ideas, they merely served to confuse me, who would have preferred a verbal exposition. It's curious that in the college where I work many students who are dyslexic or have other learning difficulties end up studying information technology in so-called flexible learning centres. Bearing in mind the statement above that "the choice of the appropriate channel is a vitally important choice in communication", it's less than obvious how a student who has difficulty reading and writing can have their needs met by a learning model which boils down in essence to 'read this; it will tell you what to write'.

Shannon-Weaver: Physical noise


Shannon is generally considered to have been primarily concerned with physical (or 'mechanical' or 'engineering') noise in the channel, i.e. unexplained variation in a communication channel or random error in the transmission of information. Everyday examples of physical noise are:

It might seem odd to use the word noise in this way, unless perhaps you're a hi-fi buff, in which case you'll be familiar with looking up the claimed 'signal-to-noise ratio' for the various bits of equipment you buy. In this technical sense, 'noise' is not necessarily audible. Thus a TV technician might speak of a 'noisy picture'. Generally speaking, in this kind of everyday communication, we're fairly good at avoiding physical noise: we shout when the motorbike goes past; you clout your little brother; cars have demisters.

However, it is possible for a message to be distorted by channel overload. Channel overload is not due to any noise source, but rather to the channel capacity being exceeded. You may come across that at a party where you are holding a conversation amidst lots of others going on around you or, perhaps, in a Communication lesson where everyone has split into small groups for discussion or simulations.

Shannon and Weaver were primarily involved with the investigation of technological communication. Their model is perhaps more accurately referred to as a model of information theory (rather than communication theory). Consequently, their main concern was with the kind of physical (or mechanical) noise discussed above.

Although physical noise and how to avoid it is certainly a major concern of scholars of communication, the Shannon and Weaver model turns out to be particularly suggestive in the study of human communication because of its introduction of a decoding device and an encoding device. The possibility of a mismatch between the two devices raises a number of interesting questions. In technological communication: I give you a PC disk and you stick it into a Mac - the Mac can't decode it; I give you an American NTSC video tape and you stick it into a European PAL video recorder - the recorder won't decode it. Transfer this notion of a mismatch between the encoding and decoding devices to the study of human communication and you're looking at what is normally referred to as semantic noise (see below). That concept then leads us on to the study of social class, cultural background, experience, attitudes, beliefs and a whole range of other factors which can introduce noise into communication.

It might be worth mentioning here, especially in connexion with the reference to the linearity of the Shannon-Weaver model, that some workers in the newly developing science of complexity have pointed to a fundamental twin flaw in our science since Newton (I am greatly simplifying here), namely that science has been concerned to understand the world using linear models and has also been concerned to discount as 'experimental noise' anything which might hinder the application of a linear model. Complexity theorists point out that when you add the noise into the system, you generally end up with something non-linear, complex, unpredictable.

Shannon-Weaver: Semantic noise


Semantic noise is not as easy to deal with as physical noise. It might not be an exaggeration to say that the very essence of the study of human communication is to find ways of avoiding semantic noise. Semantic noise is difficult to define. It may be related to people's knowledge level, their communication skills, their experience, their prejudices and so on. There is more detailed discussion of those factors in Berlo's SMCR Model.

Examples of semantic noise would include: 

Bullet.gif Distraction: You are physically very attracted to the person who is talking to you. As a result, your attention is directed to their deep blue eyes rather than what they are saying. There is no physical noise which prevents the message from reaching you. You hear it, but you don't decode it. Equally, your attention could be distracted by the other person's peculiar tics and so on. Or think of when you watched the TV news: the reporter was standing outside No.10 Downing Street, but behind him the policeman outside the door was picking his nose. As soon as the report's over you realize you haven't a clue what it was about. 
Bullet.gif Differences in the use of the code: The other person is waffling on in Aramaic about fishes and loaves. You don't understand. There is nothing which physically prevents the elements of the message from reaching you, you simply can't understand it. 
Bullet.gif Emphasising the wrong part of the message: Maybe you can think of an advertising campaign which has been so successful with some new style or gimmick that everyone is talking about it. However, no one has actually noticed what product is being advertised.
Bullet.gif Attitude towards the sender: You're talking to someone a lot older than you. On the basis of their age, you make a lot of assumptions about the kind of code appropriate to them - and the conversation goes wrong because they were the wrong assumptions.
Bullet.gif Attitude towards the message: I may have a very positive attitude to the Aramaic-speaking bearded chap in the flowing robes. But, despite that, I'd be unlikely to find him very persuasive even if he were talking to me in English about his fishes and his loaves. He believes in transcendent beings and I don't. Whilst I may respect his right to hold to what I consider to be silly convictions, I can find little respect for the beliefs themselves. So, unless he can find what I consider a more convincing explanation of this particular trick, he's wasting his breath, however convinced he may be.

Shannon-Weaver: The Decoder


Just as a source needs an encoder to translate her purposes into a message, so the receiver needs a decoder to retranslate. The decoder (receiver in Shannon's paper) is an interesting and very useful development over, say, the Lasswell Formula.

If you take a look at our discussion of the receiver, you'll see that we considered how, for example, a blind person would not have the equipment to receive whatever non-verbal messages you send in the visual channel.

The notion of a decoder reminds us that it is quite possible for a person to have all the equipment required to receive the messages you send (all five senses, any necessary technology and so on) and yet be unable to decode your messages.

An obvious example would be:

You can see it. You probably guess that it's a language, maybe even that it's Arabic. You probably don't understand it, though. In fact, it is Arabic and it does mean (but nothing very interesting). My message, encoded to you in that short sentence, cannot be decoded by you. You have the appropriate receiving equipment, but no decoder. You don't understand the code.

Can you think of where you might come across a similar inability to decode where the English language is concerned? Suppose you've been reading around Communication Studies and have come across a reference to the philosopher Immanuel Kant. So you ask your teacher about him. She replies, "Well, the Critique of Pure Reason is essentially all about answering the question: how are synthetic judgements a priori possible?" Eh? You probably have a meaning for every one of those words, except perhaps 'a priori'. You might perhaps guess that she is using the title of one of Kant's works in her answer. But the statement is incomprehensible unless you know the technical jargon of philosophy. You can't decode the message - and your teacher is a pretty lousy teacher for having failed to predict your inability to decode it (or for having accurately predicted your inability and using it as an excuse to show off!).

Those two examples may seem pretty obvious and also rather unusual. Indeed, they are, but they do serve to illustrate how communication breakdown can occur because we make the false assumption that receivers decode messages in the same way we do, that they use the code in the same way. There's a whole host of reasons why they won't - age differences, class differences, cultural differences and so on (dealt with more thoroughly in Berlo's SMCR Model).

Shannon-Weaver: The Receiver


For communication to occur, there must be somebody at the other end of the channel. This person or persons can be called the receiver. To put it in Shannon's terms, information transmitters and receivers must be similar systems. If they are not, communication cannot occur. (Actually Shannon used the term destination, reserving the term receiver for what we have called decoder. However, I think the terminology I have been using is more common in the broader understanding of 'communication theory' as distinct from Shannon's information theory.)

What that probably meant as far as he was concerned was that you need a telephone at one end and a telephone at the other, not a telephone connected to a radio. In rather more obviously human terms, the receiver needs to have the equipment to receive the message. A totally blind person has the mental equipment to decode your gestures, but no system for receiving messages in the visual channel. So, your non-verbal messages are not received and you're wasting your energy. See also the Lasswell Formula for a more detailed discussion of 'receiver'.

Shannon-Weaver: Feedback


Feedback is a vital part of communication. When we are talking to someone over the phone, if they don't give us the occasional 'mmmm', 'aaah', 'yes, I see' and so on, it can be very disconcerting. .This lack of feedback explains why most of us don't like ansaphones. In face-to-face communication, we get feedback in the visual channel as well - head nods, smiles, frowns, changes in posture and orientation, gaze and so on. Advertisers need feedback which they get in the form of market research from institutions like Gallup. How else would they know if their ads are on the right track? Broadcasters need feedback which they get from BARB's ratings. Politicians need feedback which they get from public opinion polls and so on.

Why do people often have difficulty when using computers, when they find it perfectly easy to drive a car? You'd think it should be easier to operate a computer - after all there are only a few keys and a mouse, as against levers, pedals and a steering wheel. A computer's not likely to kill you, either. It could be due to the lack of feedback - in a car, you've the sound of the engine, the speed of the landscape rushing past, the force of gravity. Feedback is coming at you through sight, hearing and touch -overdo it and it might come through smell as well! With a computer, there's very little of that.

Some years ago, our students used to play games on College computers during the lunch hour. Occasionally - if we held a lunchtime meeting, say - we would have to ask them to turn the sound off. It was amazing to see how their scores plummeted when that single channel of feedback was removed. Xerox at the Palo Alto research Centre (PARC) have been researching for years how to provide more feedback - for example, when you save a file to your hard disk, there might be a clanging noise and the more echo there is the emptier your hard disk is. You might at the moment be using a 'clicky' keyboard. There's no very good reason why a modern keyboard should make a constant clatter, but I'm used to using one at home and find it quite difficult to use keyboards which deprive me of that feedback.

Feedback is defined by the father of cybernetics, Norbert Wiener, as follows:

In its simplest form the feedback principle means that a behaviour is tested with reference to its result and success or failure of this result influences the future behaviour

Wiener (1958 : 55)

(Please note that this is translated from the German - I haven't read the original English of Wiener's book)

Well, that's the Shannon-Weaver model. Do you feel enlightened? I shouldn't imagine that any student of human-to-human communication would feel especially enlightened by Shannon's original paper, since it's all to do with information theory and, in essence, human beings don't process information, but process meanings. In the above discussion of the model I have often referred to meaning, a topic largely absent from the original model, but it is only by broadening the model to take in meaning and the biological, cognitive, technological, socio-cultural and other factors which influence it that this model can be of any use. 

Perhaps one of the main reasons for the model's popularity amongst communication theorists in the 'humanities' has been that it provides them with a ready-made jargon that ordinary mortals are not likely to be familiar with, as well as conferring on the subject a kind of pseudo-scientific respectability. Students of human communication nowadays are likely to use, at least early in their studies, terminology taken from Shannon: transmitter, receiver, channel, bandwidth, channel capacity, code, mechanical noise and so on. I suspect, however, that they are rarely required to know that i = log21/p , or that no material system can compute more than 2 x 1047 bits per second and per gram of its mass. And, if they are not required to deal with information theory in that way, then the terms 'transmitter', 'channel' and 'receiver' are just fancy words for 'speaker', 'listener' and 'air', more obfuscation than communication, a simple, but, alas, immediately suspect, means of appearing clever.

However, it has to be said that the model's separation of the communication process into discrete units has proved fruitful and has formed the basis of several other models which provide some more insightful elaboration of the human communication process. However, in disregarding meaning it may well be downright misleading. Those researchers who take this model and simply slap meaning on top of it are probably even more misleading. Some models developed upon the basic constituents of the Shannon-Weaver model are linked to below under 'related articles'. I would refer you also to the article on criticism of transmission models.

[Finally, if you've been sent to this article as a trainee teacher and find that the Shannon-Weaver contributes nothing to your understanding of the teaching/learning process, for God's sake say so.]

Related articles:

The Lasswell Formula

The Osgood and Schramm Model

Gerbner's Model

Berlo's S-M-C-R model

Maletzke's mass media model

Criticism of transmission models

Berlo on meaning

Ien Ang on Meaning

Stanley Fish on 'anti-formalism'

For further information, you may wish to consult the following websites:

Lucent Technologies' excellent website with very clear explanations

Bell Laboratories, where you can download a copy of Shannon's paper

Information Theory Society Web Page

Entropy in Information and Coding Theory

Cybernetics by Norbert Wiener - excerpts and related articles

Contribution Towards a Unified Concept of Information - doctoral thesis by Daniel Federico Flückiger, University of Berne

White Paper on Information -by Matthew G Kirschenbaum of the University of Virginia. Thought-provoking; not to be missed.