Recently many studies have been published that describe and explain how
groups of social animals make collective decisions and coordinate their actions.
However, these studies mostly focus on isolated groups, and do not consider how
these groups might behave under different social contexts, such as when there
is the threat of fighting with rival groups. In this thesis, I present two
complementary theoretical models that explore how simple differences in
leadership and decision-making dynamics within groups can have large impacts
on the investment and initiation of intergroup conflict.
In Chapter One, I present an agent-based model of intergroup conflict to
investigate how the presence of leaders and followers influences the dynamics
of conflict initiation and conflict investment. I find that changing different
parameters such as maximum group size, migration rate and intergroup
encounter rate cause either between or within group competition to be
emphasised which changes the levels of conflict investment. When between group competition is low, follower investment in conflict is low and leaders are
forced to overcompensate and contribute (“heroic leadership”). However, when
between-group competition is high, follower investment in conflict is high and
leaders can free-ride and do not contribute (“exploitative leadership”). We find
that when followers contribute then leaders are incentivised to behave more
aggressively and initiate more intergroup conflict.
In Chapter Two, I present a theoretical model to investigate how differences in
shared decision-making can influence conflict escalation in groups consisting of
leaders and followers. I find that when the sharing rules of conflict are biased
towards leaders gaining more benefits or paying less costs than followers then
leaders evolve a higher optimum for pursuing aggressive, conflict escalating
strategies. When this is true, increased shared decision-making by allowing for
increased follower control of collective decision-making results in the evolution of
more peaceful intergroup interactions. In the reverse case, when sharing rules
favour followers, then increasing their share of decision-making increases the
aggressive conflict-escalating tendencies of the group. This theoretical model
shows how different decision-making and political structures can be important for
favouring the evolution of war or peace, and demonstrates how democratic peace
theory might apply to non-human animal societies without complex institutions