4.3 More Detailed Case Studies

4.3.2 BarGoer-9 at the end of the run with the friendly scheme and listening only (fr+l)

In contrast to the above case-study, this example is designed to illustrate the possibility that an agent's behaviour may appear to be embedded in a complex web of social causation but that there still may be a simple explanation of its behaviour. In this case one would not say that the agent is socially embedded if one's modelling framework allowed this simpler model. Here one could say that the detailed web of causation only implemented the simpler strategy. Thus this example illustrates the importance of relativising the concept of social embedding to the modelling framework.

At week 100 the selected talk and action expressions for the 10 agents were as below (I include them for completeness, there is no need to decode these in detail).

barGoer-3's (talk) [wentLastWeek ['barGoer-7']] barGoer-3's (action) [OR [OR [OR [friendOfMine ['barGoer-2']] [friendOfMine ['barGoer-2']]] [friendOfMine ['barGoer-5']]] [friendOfMine ['barGoer-1']]]

barGoer-6's (talk) [lessThan [numWentLastTime] [numWentLastTime]]barGoer-6's (action) [friendOfMine ['barGoer-2']]

barGoer-7's (talk) [greaterThan [10] [10]]barGoer-7's (action) [wentLastWeek ['barGoer-2']]

barGoer-4's (talk) [greaterThan [3] [3]] barGoer-4's (action) [wentLastWeek ['barGoer-2']]

barGoer-1's (talk) [saidByLast ['barGoer-3']] barGoer-1's (action) [AND [AND [saidBy ['barGoer-8']] [AND [wentLastWeek ['barGoer-2']] [wentLastWeek ['barGoer-8']]]] [AND [AND [saidBy ['barGoer-8']] [AND [NOT [wentLastWeek ['barGoer-8']]] [AND [wentLastWeek ['barGoer-8']] [AND [saidBy ['barGoer-8']] [AND [wentLastWeek ['barGoer-2']] [AND [T] [AND [wentLastWeek ['barGoer-8']] [AND [saidBy ['barGoer-4']] [AND [saidBy ['barGoer-8']] [AND [wentLastWeek ['barGoer-6']] [wentLastWeek ['barGoer-8']]]]]]]]]]]] [AND [wentLastWeek ['barGoer-8']] [AND [wentLastWeek ['barGoer-8']] [AND [AND [AND [saidBy ['barGoer-6']] [AND [AND [AND [saidBy ['barGoer-8']] [AND [NOT [wentLastWeek ['barGoer-8']]] [AND [wentLastWeek ['barGoer-8']] [AND [wentLastWeek ['barGoer-8']] [AND [saidBy ['barGoer-8']] [saidBy ['barGoer-8']]]]]]] [AND [wentLastWeek ['barGoer-6']] [AND [NOT [wentLastWeek ['barGoer-6']]] [AND [wentLastWeek ['barGoer-6']] [AND [AND [wentLastWeek ['barGoer-8']] [AND [wentLastWeek ['barGoer-8']] [AND [saidBy ['barGoer-8']] [AND [T] [T]]]]] [wentLastWeek ['barGoer-8']]]]]]] [wentLastWeek ['barGoer-8']]]] [wentLastWeek ['barGoer-8']]] [AND [saidBy ['barGoer-8']] [wentLastWeek ['barGoer-8']]]]]]]]

barGoer-8's (talk) [friendOfMine ['barGoer-4']] barGoer-8's (action) [OR [NOT [NOT [NOT [NOT [friendOfMine ['barGoer-9']]]]]] [NOT [friendOfMine ['barGoer-9']]]]

barGoer-9's (talk) [wentLastWeek ['barGoer-2']]
barGoer-9's (action) [AND [saidBy ['barGoer-7']] [wentLastWeek ['barGoer-1']]]

barGoer-10's (talk) [wentLastWeek ['barGoer-4']] barGoer-10's (action) [wentLastWeek ['barGoer-5']]

barGoer-5's (talk) [lessThan [7] [7]] barGoer-5's (action) [friendOfMine ['barGoer-2']]

barGoer-2's (talk) [saidByLast ['barGoer-10']]
barGoer-2's (action) [friendOfMine ['barGoer-5']]

Although many of these are simply reducible to True or False, others are not. I have indicated those that do not reduce to True of False, by listing them in bold. Further more, although many of these expressions remained pretty much constant over the last 10 weeks of the simulation some did not. For example the action expressions of barGoer-9 during the last 10 weeks were:

91: [AND [AND [wentLastWeek ['barGoer-1']] [AND [AND [AND [AND [saidBy ['barGoer-1']] [wentLastWeek ['barGoer-7']]] [wentLastWeek ['barGoer-7']]] [saidBy ['barGoer-7']]] [wentLastWeek ['barGoer-7']]]] [saidBy ['barGoer-1']]]

92: [AND [wentLastWeek ['barGoer-7']] [saidBy ['barGoer-7']]]

93: [AND [AND [wentLastWeek ['barGoer-7']] [AND [wentLastWeek ['barGoer-7']] [AND [saidBy ['barGoer-1']] [saidBy ['barGoer-7']]]]] [saidBy ['barGoer-1']]]

94: [AND [AND [wentLastWeek ['barGoer-7']] [AND [wentLastWeek ['barGoer-7']] [AND [saidBy ['barGoer-1']] [saidBy ['barGoer-7']]]]] [saidBy ['barGoer-1']]]

95: [AND [AND [saidBy ['barGoer-1']] [wentLastWeek ['barGoer-1']]] [AND [wentLastWeek ['barGoer-7']] [saidBy ['barGoer-1']]]]

96: [saidBy ['barGoer-7']]

97: [AND [wentLastWeek ['barGoer-7']] [AND [wentLastWeek ['barGoer-7']] [AND [saidBy ['barGoer-1']] [saidBy ['barGoer-7']]]]]

98: [AND [saidBy ['barGoer-7']] [saidBy ['barGoer-1']]]

99: [AND [wentLastWeek ['barGoer-7']] [AND [wentLastWeek ['barGoer-7']] [AND [saidBy ['barGoer-1']] [saidBy ['barGoer-7']]]]]

100: [AND [saidBy ['barGoer-7']] [wentLastWeek ['barGoer-1']]]

Each time barGoer-9's action expression is a conjunction of saidBy or wentLastWeek primitives referring to agents barGoer-1 and barGoer-7. Each time [wentLastWeek [`barGoer-1']] and [saidBy [`barGoer-7']] would evaluate to False and [wentLastWeek [`barGoer-7']] and [saidBy [`barGoer-1']] to True, so its continued non-attendance depends upon the presence of either of a [wentLastWeek [`barGoer-7']] or [saidBy [`barGoer-1']] in the chosen conjunction.

But in this run of the simulation there is a far simpler explanation for bar-Goer-9's behaviour: that is because it has only two `friends' (barGoer-10 and barGoer-3) it is not worth its while to attend. In fact this is true for each agent - its attendance pattern can be explained almost entirely on the number of friends it has (figure 4 shows the imposed friendship structure for this run). This is shown in table 5. Only bar goers 3, 8 and 7 need further explanation. BarGoer-7 has three friends but none of these are `loners' like barGoer-9 (i.e. only having 2 friends), so there is a good chance that three of its friends will go while barGoer-3 and 8 both have a friend who is a loner. The behaviour with period 6 probably arises due to the fact that agents evaluate their strategies over the arises because agents evaluate their expressions only up to a horizon of five time periods into the past*1.

Thus in this case we have a simple explanation of barGoer-9's continued absence from the bar in terms of its own likely utility due to the limited number of friends it has*2. The friendship structure in this run was the one illustrated in figure 4. Agents barGoer-3 and 8 are more embedded that the others at the end of this run as the explanation of their behaviour has to include each other and the fact that they have friends who only have two friends.

Capturing Social Embeddedness: a constructivist approach - Bruce Edmonds - 30 OCT 98

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