Figure 2. Relationship between threshold discount factor (
) and cost-to-benefit ratio (
).
I use the five types of networks and set (a) 
, 
, and (b) 
, 
. The results for direct reciprocity (i.e., 
) and upstream reciprocity on the directed triangle (i.e., 
) are also shown by thin black lines for comparison. In (a), I set the rewiring probability for the WS model to 
and 
. For the BA model, there are initially 
nodes (i.e., dyad), and the number of links that each added node has is set to 
. For my variant of the KE model, the initial number of nodes and the number of links that each added node has are set to 
, and an active node 
is deactivated with probability proportional to 
, where 
. After constructing the network based on the original KE model [34], I rewire fraction 
of randomly selected links to make the average distance small. In (b), I set 
and 
for the WS model, 
for the BA model, and 
and 
for the KE model.