  Incentives are more likely to elicit desired outcomes when they are designed
based on accurate models of agents' strategic behavior. A growing literature,
however, suggests that people do not quite behave like standard economic agents
in a variety of environments, both online and offline. What consequences might
such differences have for the optimal design of mechanisms in these
environments? In this paper, we explore this question in the context of optimal
contest design for simple agents---agents who strategically reason about
whether or not to participate in a system, but not about the input they provide
to it. Specifically, consider a contest where $n$ potential contestants with
types $(q_i,c_i)$ each choose between participating and producing a submission
of quality $q_i$ at cost $c_i$, versus not participating at all, to maximize
their utilities. How should a principal distribute a total prize $V$ amongst
the $n$ ranks to maximize some increasing function of the qualities of elicited
submissions in a contest with such simple agents?
  We first solve the optimal contest design problem for settings with
homogenous participation costs $c_i = c$. Here, the optimal contest is always a
simple contest, awarding equal prizes to the top $j^*$ contestants for a
suitable choice of $j^*$. (In comparable models with strategic effort choices,
the optimal contest is either a winner-take-all contest or awards possibly
unequal prizes, depending on the curvature of agents' effort cost functions.)
We next address the general case with heterogeneous costs where agents' types
are inherently two-dimensional, significantly complicating equilibrium
analysis. Our main result here is that the winner-take-all contest is a
3-approximation of the optimal contest when the principal's objective is to
maximize the quality of the best elicited contribution.
