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256 Socially Intelligent Agents

Figure 31.1. Distance between 2 agents in bilateral negotiation

agents preferred to negotiate with one another and each was able to offer to
change one or more of its least important positions in exchange for the other
agent agreeing one of its more important positions.
Once any pair or larger group of agents fully agrees on all positions, they
form a coalition to negotiate with agents not in the coalition or with other
coalitions. The process ends when all agents are members of a single coalition
or super-coalition (i.e. coalition of coalitions of coalitions ...). In practice, the
only simulated negotiation processes that reached a conclusion were all of the
two-agent processes.

3. Simulation Results

Theprogressof bilateral negotiationwas represented by changesin thediffer-
ences of negotiating positions of two agents. These differences were measured
as the Euclidian distance between the two position strings interpreted as co-
ordinate vectors in a 30-dimensional hyperspace. An example of the progress
represented by this measure is given in Figure 31.2. This progress is typical of
all runs with two negotiating agents. The range of the number of cycles elapsed
before agreement was reached was from 8 to 12 with the bulk of the distance
eliminated in the last half or less of the cycles. There was no learning for the
agents to do since they had no choice of negotiating partners.
Although simple negotiating strategies work well for the modelled bilateral
negotiation, they do not work at all in simulations of multilateral negotiation