Abstract
When a log burns, it transforms from a block of wood into a pile of ash. Such state-changes are among the most dramatic ways objects can change their appearance—going beyond mere changes of position or orientation. How does the mind represent changes of state? A foundational result in visual cognition is that memory extrapolates the positions of moving objects—a distortion called “representational momentum.” Here, we exploited this phenomenon to investigate mental representations in “state-space.” We created realistic animations of objects undergoing state-changes: ice melting, grapes shriveling, logs burning, etc. Participants observed interrupted segments of these animations, and then reported the last frame they saw using a slider. Four experiments showed representational momentum for state-changes, revealing dynamic representation of physical states. In Experiment 1, participants consistently reported a frame more “forward” in time (e.g., more melted) than they had actually seen. Experiment 2 showed that such representations are flexible, arising even for directions rarely encountered before: We included both forward- and backward-playing animations (e.g., both melting and “unmelting”) and observed representational momentum in both directions (e.g., for backward animations, participants remembered the ice as more “unmelted” than it really was). Experiment 3 controlled for low-level motion cues by showing that even a single static frame elicits representational momentum: Participants who saw one frame of each state-change misremembered it as further along its implied state-transformation. This also indicates that the mind privileges the physically natural forward direction. Finally, Experiment 4 ruled out biases that may have arisen from the response method (slider adjustments) by replicating our earlier results using a two-alternative forced-choice paradigm. Taken together, our findings reveal that mental representations of a dynamic world actively incorporate such dynamic changes, and in surprisingly broad ways: Whether in position or state, the mind extrapolates how objects change.