  One of the most striking features of human cognition is the capacity to plan.
Two aspects of human planning stand out: its efficiency and flexibility.
Efficiency is especially impressive because plans must often be made in complex
environments, and yet people successfully plan solutions to myriad everyday
problems despite having limited cognitive resources. Standard accounts in
psychology, economics, and artificial intelligence have suggested human
planning succeeds because people have a complete representation of a task and
then use heuristics to plan future actions in that representation. However,
this approach generally assumes that task representations are fixed. Here, we
propose that task representations can be controlled and that such control
provides opportunities to quickly simplify problems and more easily reason
about them. We propose a computational account of this simplification process
and, in a series of pre-registered behavioral experiments, show that it is
subject to online cognitive control and that people optimally balance the
complexity of a task representation and its utility for planning and acting.
These results demonstrate how strategically perceiving and conceiving problems
facilitates the effective use of limited cognitive resources.
