Where does message collide?

In Shannon's 1948 A Mathematical Theory of Communication, a message is one item selected from a set of possible messages at a source, to be reproduced at a destination after travelling through a channel. Shannon set aside what a message means: for the engineering problem the only fact that matters is which item was chosen from the known set, and how many choices the set allows. Shannon and Weaver's 1949 book The Mathematical Theory of Communication made this framing widely read. Here a message is a formal selection whose size is measured in bits, not the meaningful content a person composes and not a molecule inside a cell.[1][2]

Unit

One selection from a set of possible messages, its size given in bits

Recovery means

Not applicable

Measured by

Quantified by the number of possible messages and their probabilities, yielding entropy in bits

Lasswell's 1948 essay The Structure and Function of Communication in Society framed communication as who says what, in which channel, to whom, with what effect: the "what" is the message, the content passed from a source to an audience. Berlo's 1960 The Process of Communication made the message one of four named elements alongside source, channel, and receiver, and broke it into its content, its code, and its treatment. The referent is meaningful symbolic content that one party encodes for another to interpret, where the meaning is the whole point, unlike the meaning-blind selection of information theory or a strand of nucleic acid in a cell.[3][4]

Unit

One piece of symbolic content sent from a source to a receiver

Recovery means

Not applicable

Measured by

Studied by content analysis of the message and by what receivers understand from it

Jacob and Monod's 1961 Genetic Regulatory Mechanisms in the Synthesis of Proteins proposed a short-lived messenger that carries the genetic message copied from a gene to the ribosomes, where proteins are assembled. Brenner, Jacob, and Meselson's 1961 An Unstable Intermediate Carrying Information from Genes to Ribosomes for Protein Synthesis gave the experimental evidence for this messenger RNA. Here the message is a sequence of bases transcribed from DNA and read three letters at a time into protein, a physical molecule inside a cell rather than a mathematical selection or the symbolic content of human speech.[5][6]

Unit

One messenger RNA transcript, a base sequence copied from a gene

Recovery means

The transcript is degraded after use, so the message is transient and must be remade from the gene

Measured by

Detected and quantified by sequencing and by measuring transcript levels in the cell