Forward false memories of actions only occur for single and simple actions

Observing a photo depicting an individual about to perform an action can implicitly trigger an automatic forward mental simulation of the action's unfolding. Since automatic processes can lead to errors in source monitoring (i.e. confusing self-generated information with perception), we investigated the tendency to form false memories of forward compared to backward phases of actions. In Experiment 1, participants were presented with a series of static photos depicting unfolding actions on objects (e.g. blowing the nose), and in Experiment 2 they were presented with more complex actions in a naturalistic context (i.e. actions composed of three different sub-actions such as making coffee). In both experiments, fifteen minutes after encoding, participants completed a recognition task in which they were shown photos representing moments that were temporally distant (backward or forward in time) from the original photos, along with the same photos seen at encoding. Results revealed that participants were more likely to accept forward photos as seen compared to backward photos for simple actions, whereas this effect was absent for complex actions. In Experiment 3, we directly manipulated the complexity of actions in a single experiment and replicated the previous results. Our findings suggest that false memories due to implicit forward simulations only occur for simple actions when the action direction is mandatory. In contrast, complex actions might engage different mechanisms, such as higher-level event processing, which is easier to monitor and might reduce memory distortions. These insights expand our understanding of memory distortions for actions and highlight the role of action complexity in shaping the mechanisms of mental simulation.