Abstract
In order to engage with the objects we encounter in everyday life we must have accurate estimates of their physical properties (e.g. size, weight, slipperiness, and deformability). How do we discover this information? In some cases, an object’s physical properties are readily observable or can be inferred based on previous experience with similar objects. In other cases, latent physical attributes are not accessible to visual inspection alone – for example, a box may be light or heavy depending on its contents. We can learn about latent physical variables by interacting with objects, but there are many more objects in our daily environments than we can interact with directly. Can we also learn about the physical properties of objects by observing others interacting with them? Here, we tested participants’ ability to infer the weights of visually indistinguishable containers by watching actors lift them. Stimuli consisted of video clips of four actors lifting a set of metal canisters that were identical in appearance but varied in weight from 100–900 grams in increments of 100g. On each trial, participants were presented with a pair of lifting clips and asked to determine which canister was heavier. We found that participants were readily able to discriminate even small differences in the lifted weights, even without any training. Strikingly, participants were just as good at discriminating the weights of objects lifted by two different actors as they were when viewing two clips from the same actor, indicating that they can capitalize on visual cues to weight that are common across actors rather than idiosyncratic to the lifting behavior of particular individuals. These findings demonstrate that we can use our perception of others’ behaviors to learn about the physical structure of the environment, and point toward a key role of action observation in physical scene understanding.