Posted by Yogesh Malhotra on March 03, 1998 at 21:12:02:

In Reply to: Re: Information Theory: What Weiner Really Said posted by Yogesh Malhotra on March 03, 1998 at 20:49:58:

Review of:

MacKay, D.M. (1969). Information, Mechanism and Meaning, Cambridge, MA: The MIT Press.

Why should we need to measure information: the method which gives us the maximum amount of information for a given outlay of time or space or other resources. [Is more information good? Information deficit vs. Information overload.]

What we mean by information? Roughly speaking, we say that we have gained information when we know something now that we didn't know before, when 'what we know' has changed. In a technical sense, 'information' implies: that which enables us to make a selection from a set of possibilities or to narrow the range of possibilities about which we are ignorant . The number of choices is at a minimum if at each stage we arrange to choose between two equally likely possibilities. "Selective information- content" is the equivalent number of independent choices between equally likely alternatives.

The theory of information is first and foremost a linguistic tool. It enables us to speak precisely and quantitatively where previously we have had to speak vaguely and qualitatively.

The general information theory is concerned with the problem of measuring changes in knowledge. It key is the fact that we can represent what we know by means of pictures, logical statements, symbolic models, etc.

While theory of communication (referred to by some as Information Theory, but never so by Shanon, its chief originator) is based on the concept of 'communication' as the replication of what is transmitted by the sender. Communication is the activity of replicating information.

The founders of the theory of information have insisted that the "amount of information" (or, better, the selective information-content) of a signal, as they define it, bears no direct relation to the semantic function of the signal. The trouble here appears to be due largely to a confusion of the concept of information with that of information- content -- the confusion of a thing with a measure of a thing (??). Communication engineers have not developed a concept of information at all. They have developed a theory dealing explicitly with only one particular feature or aspect of messages "carrying" information -- their unexpectedness or surprise value.

Semanticists on the other hand are concerned with different features of information, such as its logical complexity and its meaning. But both engineers and semanticists have in mind the same concept of information. Both mean by information that which promotes or validates representational activity (activity from which it is possible to infer something about some other state of affairs). Both are entitled to regard the function of information as to be selective: to prescribe choice or decision.

McKay argues that the connection between statistical and semantic features of information cannot but be indirect, these are features of one and the same central concept. I have gained information when I know something that I didn't know before: when what I know has changed. Fundamentally, it implies that in some circumstance or other my expectations will be different. I am now conditionally ready to react differently. Information in fact could be defined in actor-language as that which alters my total state of adaptive readiness in this sense. What is internally imitated is not a static structure of relations between things, so much as the dynamic structure of relations between events. Events of perception are what we know primarily, and what is organised as we receive information is our conditional readiness to match the pattern of events of perception by the pattern of our own internal or external reaction.

The meaning of a signal to a given receiver (in observer-language) may be defined as the selective operation which the signal defines (in a logical, not a physical sense) on the set of possible states of readiness. The selective information-content for the receiver as defined in communication theory is a logarithmic measure of the unexpectedness of that selective operation. Thus we can readily see why even to the receiver the selective information content is not directly related to the meaning (p. 71).

• Yogesh Malhotra

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Follow Ups:

• Thought on readings Tom Sudman 10:55:38 3/05/98 (9)
  • Re: Data, Information & Knowledge Yogesh Malhotra 10:44:57 3/07/98 (8)
    • Re: Data, Information & Knowledge Craig Maudlin 20:59:36 3/10/98 (7)
      • Re: Data, Information & Knowledge Ross Hall 13:20:39 3/11/98 (6)
        • Re: Data, Information & Knowledge Craig Maudlin 18:39:00 3/11/98 (5)
          • Re: Difficulties with Information Theory Yogesh Malhotra 23:15:05 3/11/98 (4)
            • Re: Difficulties with Information Theory Craig Maudlin 19:18:03 3/12/98 (3)
              • Re: Difficulties with Information Theory Tom Sudman 14:23:17 3/16/98 (0)
              • Re: Difficulties with Information Theory Mezei 22:27:13 3/12/98 (1)
                • Re: Difficulties with Information Theory Martyn R Jones 08:26:34 3/25/98 (0)

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