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can transmit. That is, given a particular signal C0039-01.gifat time t, the ith component Ii(t) is the value di(t)of the ith sensor at time t. In general the sets Ii may be quite different, corresponding to different kinds of sensors or sensory modalities.
The formal presentation of an adaptive plan t can be simplified by requiring that C0031-01.gifserve as the state of the plan at time t. That is, in addition to being the structure tried at time t, C0031-01.gif must summarize whatever accumulated information is to be available to t. We have just provided that the total information received by t up to time t is given by the sequence C0039-04.gif. Generally only part of this information is retained. To provide for the representation of the retained information we can make use of the latitude in specifying C0021-03.gif. Think of C0021-03.gifas consisting of two components C0039-11.gif and C0039-02.gif, where C0039-12.gifis the structure tested against the environment at time t, and the memory C0039-03.gifrepresents other retained parts of the input history C0039-04.gif. Then the plan can be represented by the two-argument function
C0039-05.gif
Here the structure to be tried at time t + 1, C0039-13.gif, along with the updated memory C0039-14.gif, is given by
C0039-06.gif
(The projection of t on C0039-02.gif,
C0039-07.gif
defined so that
C0039-08.gif
is that part of t which determines how the plan's memory is updated.) It is clear that any theorems or interpretations established for the simple form
C0039-09.gif
can at once be elaborated, without loss of generality or range of application, to the form
C0039-10.gif
Thus the framework can be developed in terms of the simple, two-argument form of t, elaborating it whenever we wish to study the mechanisms of trial selection or memory update in greater detail.

 
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