  Collective risk dilemmas (CRDs) are a class of n-player games that represent
societal challenges where groups need to coordinate to avoid the risk of a
disastrous outcome. Multi-agent systems incurring such dilemmas face
difficulties achieving cooperation and often converge to sub-optimal,
risk-dominant solutions where everyone defects. In this paper we investigate
the consequences of risk diversity in groups of agents learning to play CRDs.
We find that risk diversity places new challenges to cooperation that are not
observed in homogeneous groups. We show that increasing risk diversity
significantly reduces overall cooperation and hinders collective target
achievement. It leads to asymmetrical changes in agents' policies -- i.e. the
increase in contributions from individuals at high risk is unable to compensate
for the decrease in contributions from individuals at low risk -- which overall
reduces the total contributions in a population. When comparing RL behaviors to
rational individualistic and social behaviors, we find that RL populations
converge to fairer contributions among agents. Our results highlight the need
for aligning risk perceptions among agents or develop new learning techniques
that explicitly account for risk diversity.
