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The following technical report (CS-90-99) is available.

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  Evolution of Communication in a Population of Simple Machines

                         Bruce MacLennan
                 Department of Computer Science
                   The University of Tennessee
                    Knoxville, TN 37996-1301
                    Technical Report CS-90-99

                            ABSTRACT

We show that communication may evolve in a population of simple
machines that are physically capable of sensing and modifying a
shared environment, and for which there is selective pressure in
favor of cooperative behavior.  The emergence of communication
was detected by comparing simulations in which communication was
permitted with those in which it was suppressed.  When communica-
tion was not suppressed we found that at the end of the experi-
ment the average fitness of the population was 84% higher and had
increased at a rate 30 times faster than when communication was
suppressed.  Furthermore, when communication was suppressed, the
statistical association of symbols with situations was random, as
is expected.  In contrast, permitting communication led to very
structured associations of symbols and situations, as determined
by a variety of measures (e.g., coefficient of variation and
entropy).  Inspection of the structure of individual highly fit
machines confirmed the statistical structure.  We also investi-
gated a simple kind of learning.  This did not help when communi-
cation was suppressed, but when communication was permitted the
resulting fitness was 845% higher and increased at a rate 80
times as fast as when it was suppressed.  We argue that the
experiments described here show a new way to investigate the
emergence of communication, its function in populations of simple
machines, and the structure of the resulting symbol systems.