  Human dynamics is known to be inhomogeneous and bursty but the detailed
understanding of the role of human factors in bursty dynamics is still lacking.
In order to investigate their role we devise an agent-based model, where an
agent in an uncertain situation tries to reduce the uncertainty by
communicating with information providers while having to wait time for
responses. Here the waiting time can be considered as cost. We show that the
optimal choice of the waiting time under uncertainty gives rise to the bursty
dynamics, characterized by the heavy-tailed distribution of optimal waiting
time. We find that in all cases the efficiency for communication is relevant to
the scaling behavior of the optimal waiting time distribution. On the other
hand the cost turns out in some cases to be irrelevant depending on the degree
of uncertainty and efficiency.
