3. The Code Model Decoded 67
If the transmitter and receiver cannot equally handle the message, then the receiver has no means of confidently assessing the resemblance between the original and
constructed messages. Shannon’s theory is ultimately a theory of probability, and probability depends upon the ability to statistically measure the likelihood of an event’s
being attributable to chance. This is why information, in this context, is sometimes defined as “a measure of uncertainty”
Chater 1994 :1685 or as “the ability to make
nonrandom selections from some set of alternatives” Reddy 1979
. The ability of the transmitter and receiver to operate effectively together i.e., for the transmitter to
successfully read a primary message and transmit a corresponding signal, and for the receiver to successfully receive that signal and construct a message closely corresponding
to that handled by the transmitter fundamentally depends upon the transmitter and receiver having identical copies of the code.
3.2.3.1.4. Code
As has been presented, there has been great confusion regarding the concepts of information and message. It should come as no surprise that there is also confusion
regarding the concept of code. As Wales recounts, the term “is so widely used in other fields, linguistic and literary, that it is in danger of becoming a mere synonym for
language, variety, or dialect”
1994 :577. In the context of information theory, the idea is
quite distinct from any of these uses. The problem again stems from distinctions between the technical and common uses of the word.
In the common definition of the term, the code is considered to be “a set of signals for sending messages”
Neufeldt 1989 :84. In this common definition, the “set of signals”
is an alphabet, albeit one devised of potentially mobile components, such as electrons or wave energy. As has been discussed, however, such a definition will not hold for infor-
mation theory, for in the context of that theory the message is not sent anywhere.
What then is the code as defined in information theory? In information theory the code is not an alphabet, but rather an algorithm, a “systematic method of solving a certain
kind of mathematical problem” Neufeldt 1989
:11. In the context of communication systems that “problem” is the relationship between the two alphabets, the message
alphabet and the signal alphabet. The code, then, is the algorithm that defines the relationship between the two alphabets. The actual signals selected must thereby be
selected from a set of possible signals, just as the actual message must be selected from a set of possible messages.
The set of possible signals is constrained both by mechanical potential and practical constraints on the system. The mechanical capabilities of the transmitter and receiver are
the primary concern. Obviously, it would be impossible for the set of possible signals to include a signal that the system was incapable of transmitting. For practical reasons, such
as maximal contrast, systems typically employ only a subset of the total possible signals. This subset may be spoken of as the repertoire of signal characters
Reddy 1979 .
68 3. The Code Model Decoded
In speaking of the information theoretic definition of ‘message’, it is important to differentiate the primary message from the constructed message. By definition, these
messages are not mobile, while the signal is mobile. If the primary message is to be subjected to the communication process, then the system must “read” that message and,
in response, assemble a corresponding set of “characters” selected from the signal alphabet. The transmitter employs the code in determining what subset of the signal-
alphabet characters it will include in the signal to be sent. Similarly, the receiver employs the code in determining what subset of message-alphabet characters it will include in the
constructed message.
As mentioned, the technical definition of code as algorithm is sometimes entangled with the common definition as a set of signals for sending messages. For example,
Wales writes, “One way of looking at a code is to see it as a sign system primary code that can be used to convert messages into another secondary code. So, verbal language
is the basis of Morse Code”
1994 :577. Wales is quite correct in pointing out the exist-
ence of two systems i.e., the message alphabet and the signal alphabet, but unfortu- nately confuses the issue in referring to the alphabets as codes. Additional confusion
arises from the fact that, strictly speaking, in using the example of Morse Code, she refers to a code designed to handle messages composed of characters from the Roman alphabet,
rather than messages “written” in verbal language. The confusion is further compounded by the metonymy involved; in common language the term “Morse Code” is typically
used in referring to both the algorithm and the signal alphabet.
The issue of code and message provides another distinction as defined within information theory: while the constructed message is directly related to the code handled
by the receiver, the original message is not necessarily so related to the code handled by the transmitter.
In Shannon’s model this distinction occurs in isolation of the information source and the transmitter. This is an important distinction, for in contrast to a strict
information theoretic perspective, the code-model view of communication typically combines
information source and transmitter into one unit, the ‘encoder’. As stated, an awareness of the set of possible messages may constrain the types of messages that are
assembled, but the code itself is not employed in construction of the primary message. In the example scenario provided earlier, the telegraphic system may constrain the type of
signal the woman is able to effectively “send,” but the code itself is not involved in the message construction. The telegraph operator does not read the message for content,
evaluating whether or not it is a good love letter or whether it adequately expresses the woman’s thoughts. He simply accepts or rejects the characters she provides, based upon
their compatibility with the code requirements.
As is seen in Wale’s 1994
:577 comment quoted previously, to some extent the telegraphy example hinders explanation of this process, for in the example a separate
“coding” event actually precedes the written message. Describing the process of human speech production in terms of the Shannon’s model of communication, one might say that
the woman had a thought a semantic concept in mind. In relation to that thought, she produced a primary message an organized assemblage, i.e., a “text”. That message was
3. The Code Model Decoded 69
then processed via a code and a signal was assembled that corresponds, within the limita- tions of the system, to her original message. That signal is typically composed of one or a
combination of the following:
a Coordinated movements of the vocal articulators and diaphragm in turn producing the movement of air and resulting sound waves, including pitch and
intonation b Coordinated movements of the hands and fingers as they hold a writing
instrument, manipulate a keyboard, or articulate a signed language c Gestures and body movements, including facial postures and eye movements
The primary message text is related to the vocal or dextral movements via a code, but that code was not involved in the assembly of that message. This is not to say that an
awareness of the coding possibilities did not factor into the assemblage. Rather, it is to point out that the construction of the primary message and the construction of the signal
are separate events.
The system is not responsible for assembling the primary message. Neither is the system responsible for defining a relationship if there is one between the
primary message and the semantic concepts conceived by the speaker. The system is, however, responsible for assembling the constructed message also a text, and it does
employ the code in that process. The system is not, however, responsible for defining a relationship between the constructed message and any semantic concepts conceived by
the hearer.
With this explanation in view, it should be clear that there is only one area in which the model of communication proposed in Shannon
1948 ,
1949 can be legitimately
applied to human oral communication: articulatory and acoustic phonetics and their relationship to phonology. The transmitter handles articulation and the receiver handles
auditory reception. Shannon’s theory would then be concerned with the accuracy to which the speaker can “read” an articulatory-text that is, a string of phonemes and
transmit a sequence of sound waves, which, in turn, the receiver can hear and “write” i.e., construct a corresponding acoustic-text also a string of phonemes.
As has been addressed, it is a condition of Shannon’s theory that the transmitter and receiver have the same code. But this says nothing about the semantic perceptions of the
hearer i.e., meaning. Shannon’s theory does not address these. This is an important distinction that has been historically neglected by linguists. Undoubtedly the interference
posed by Saussure’s speech circuit contributes to that oversight. The integration of the Saussurean speech circuit with information theory will be addressed in section
3.3.3 .
3.2.3.2. A brief review of Weaver’s contributions
