In the book, Wiener helped define the new quantitative concept of information coming out of the work of John von Neumann, Alan Turing, and Claude Shannon on computers and communications.

As Leo Szilard had done twenty years earlier, Wiener emphasized the information gained in choices between two equiprobable alternatives, which produce "bits" (binary digits) of information.

One and all, time series [of experimental data] and the apparatus to deal with them, whether in the computing laboratory or in the telephone circuit, have to deal with the recording, preservation, transmission, and use of information. What is this information, and how is it measured? One of the simplest, most unitary forms of information is the recording of a choice between two equally probable simple alternatives, one or the other of which is bound to happen — a choice, for example, between heads and tails in the tossing of a coin. We shall call a single choice of this sort a decision. If then we ask for the amount of information in the perfectly precise measurement of a quantity known to lie between A and B, which may with uniform a priori probability lie anywhere in this range...

We may conceive this in the following way: we know a priori that a variable lies between 0 and 1, and a posteriori that it lies on the interval (a, b) inside (0, 1). Then the amount of information we have from our a posteriori knowledge is

-log₂ (measure of (a, b) / measure of (0, 1))

Wiener's negative of the entropy led Leon Brillouin to coin the term negentropy

The quantity we here define as amount of information is the negative of the quantity usually defined as entropy in similar situations. The definition here given is not the one given by R. A. Fisher for statistical problems, although it is a statistical definition; and can be used to replace Fisher's definition in the technique of statistics.

(Cybernetics, 2nd edition, pp.61-62)

As a final remark, let me point out that a large computing machine, whether in the form of mechanical or electric apparatus or in the form of the brain itself, uses up a considerable amount of power, all of which is wasted and dissipated in heat. The blood leaving the brain is a fraction of a degree warmer than that entering it. No other computing machine approaches the economy of energy of the brain. In a large apparatus like the Eniac or Edvac, the filaments of the tubes consume a quantity of energy which may well be measured in kilowatts, and unless adequate ventilating and cooling apparatus is provided, the system will suffer from what is the mechanical equivalent of pyrexia, until the constants of the machine are radically changed by the heat, and its performance breaks down. Nevertheless, the energy spent per individual operation is almost vanishingly small, and does not even begin to form an adequate measure of the performance of the apparatus. The mechanical brain does not secrete thought "as the liver does bile," as the earlier materialists claimed, nor does it put it out in the form of energy, as the muscle puts out its activity. Information is information, not matter or energy. No materialism which does not admit this can survive at the present day.

(Cybernetics, 2nd edition, p.132)