Edited sentence: I believe that it is possible to gain some clarity by considering connectivity.I hypothesise that an individual agent can only have a certain number of connections to other agents (with human agents this number will change according to the state of the individual and also the state of the environment).If all connections are made within the group it forms a closed system.We can then think of the strength of a group's boundaries as the proportion of connections which are made within the group - the greater the proportion, the stronger the group boundaries.We often hear of groups having "strong" or "weak" boundaries but without any clear sense of the meaning