Abstract
What we do depends on what we know. But what if we wish to decouple our behavior from our knowledge, by appearing not to know something that we really do? Such pretense behavior relies on counterfactual self-simulation — an understanding of how we would behave if our knowledge were different — and so provides an opportunity to investigate how well people can emulate a hypothetical knowledge state. Here, we examined the ability to both produce and visually detect pretense behaviour, using the game "Battleships". Normally, "Battleships" is played by searching for ships hidden behind cells in a grid. In our studies, we instead showed subjects where all the ships were but asked them to play as if they didn’t see our hints and were ignorant of the ships' locations. Analyzing non-pretend (regular) games of the same subjects, we identify robust behavioural patterns in the location and timing of cell selections, including serial dependencies in hit probability and decision time, and an association between decision time and the entropy of the posterior distribution over candidate actions. Critically, we show that pretend games demonstrate similar, but exaggerated, behavioural patterns. By comparing pretend and non-pretend games to the modeled behaviour of a near-optimal Bayesian agent, we find that pretend behaviour is markedly less optimal than non-pretend behaviour. This is because pretenders often play in ways that don’t make sense given the limited knowledge they pretend to have. However, despite these striking differences, independent "judge" participants were completely unable to discriminate the games of pretenders from non-pretenders. Thus, while pretenders behave in ways that could reveal their pretense to a keen eye, these subtle patterns are not detected by naïve observers. We conclude by discussing the implications of our findings for simulation accounts of theory of mind and metacognition.