ScienceDaily reported (here) on a study by E. Morsella, The Essence of Conscious Conflict: Subjective Effects of Sustaining Incompatible Intentions.
The results demonstrated that merely preparing to perform an incompatible action, for example preparing to move simultaneously left and right, triggered stronger changes in awareness than preparing to perform a compatible action or experiencing a conflict that does not engage the muscles that move our bodies.
Projecting our actions into the near future would be a good way to identify impossible combinations of actions. Heightened awareness of these conflicts would highlight the problems. Morsella proposes a theory which predicts that the primary role of consciousness is to bring together competing demands on skeletal muscle.
If the brain is like a set of computers that control different tasks, consciousness is the Wi-Fi network that allows different parts of the brain to talk to each other and decide which action ‘wins’ and is carried out… The study finds that we are only aware of competing actions that involve skeletal muscles that voluntarily move parts of the body, the bicep for example, rather than the muscles in the digestive tract or the iris of the eye….The results give credence to an interesting idea that ‘thinking is for doing,’ a framework psychologists are using to explore the link among consciousness, perception and action.