< previous page page_128 next page >

Page 128
of loss when P(x, t) is near one. But as t advances ct® 0, so that
C0144-04.gif
and the rate of change approaches [µx(t)/µ(t)] - 1. In particular, if some schema begins to occupy a large fraction of the population (through consistent above-average performance) its rate of increase will come very close to [µx(t)/µ(t)] - 1.
We can now go on to determine the number of trials allocated to the observed best schema as a function of the number of trials allocated to structures which are not instances of x. In this determination C0144-09.gif designates the number of structures in C0144-06.gif which are not instances of schema x. C0144-10.gif and C0144-11.gif designate the number of trials allocated from t0 to t to structures which are, respectively, instances of x and not instances of x. (That is, C0144-12.gif, for t ³ t0.) The logarithm of the effective payoff to x or log payoff, bounded below by C0144-13.gif, plays a direct role in
LEMMA 7.3: If each instance of x gives rise, on the average, to at least one new instance of x in each generation over the interval (t0, t), i.e., if C0144-07.gifC0144-08.gif, then the trials from t0 onward satisfy
C0144-03.gif
where C0144-05.gifis (a lower bound on) the average log payoff over (t0, t).
Proof:
C0144-01.gif
However,
C0144-02.gif

 
< previous page page_128 next page >

If you like this book, buy it!