Pretending not to know reveals a powerful capacity for self-simulation

Feigning ignorance is crucial in contexts as diverse as diplomacy, warcraft and personal relationships, each demanding strategic concealment of information. To be effective, such ‘epistemic pretense’ requires us to anticipate how we would behave with different knowledge, and then to act in accord with that counterfactual knowledge state. Decades of research on hindsight bias suggest that people are poor at appreciating how they would behave when ignorant. In stark contrast, here we discover a remarkable capacity to simulate decision-making under a counterfactual knowledge state, by comparing real and ‘pretend’ play in two large-scale gamified experiments. Subjects saw the full solution to a game (e.g., all ship locations in Battleship, or the hidden word in Hangman) but then attempted to play as though they didn’t have this information. Impressively, they mimicked broad and subtle patterns of ordinary play, completely convincing peers of their ignorance. Nevertheless, computational modeling uncovered traces of ‘over-acting’ in their decisions, consistent with a schematic simulation of their minds. Opening up a new approach to studying self-simulation, our results reveal intricate metacognitive knowledge about decision-making, drawn from a rich—but simplified—internal model of cognition.