9.4 LEARNING FROM THE MISSION MODELLet us now run the model a couple of times (preferably at slower speeds, which
can be selected by moving the speed slider to the left) and see what happens.^7
With the initial parameter settings (mission-goal = 100 percent, conversion-
rate = 0.1, learning =“any”, apostles = 0),^8 all households are converted
typically in less than 150 days. The plot diagram (see Figure 9.2) also shows
that the movement does not grow at a steady pace. In the beginning, the speed
of growth is relatively slow. With only a few converted households, the
“pagans”do not have many neighbors from whom they can be informed
about the Jesus followers’message. However, as more and more households
become followers, the number of new households being informed grows and
the movement grows fast. In the last phase, the number of remaining pagan
households is limited and the speed of growth is correspondingly slower. That
is, even if the exposure of the remaining households to the innovation is
maximal, there are only few conversions on each day. The process we have
just described is an example of the general phenomenon of logistic growth
(Strogatz, 2000, pp. 21–4), which applies to many growth processes in the real
world, including the spread of innovations, the spread of viruses, or the
expansion of a species in a habitat.
Followers50010001500200025000
020406080100120140
Days
Figure 9.2.The growth of the Christian movement in the“Mission”model.(^7) Tip: It is a good idea to set the speed higher for the setup procedure and then set it lower
before pushing the go button.
(^8) NB. The parameter“prestige-bias”is ignored if there are no apostles in the model.
196 Cognitive Science and the New Testament