Visually simulated altered gravity modulates perceived object weight.

Gravity is a fundamental force acting on all objects on Earth. It is therefore unsurprising that the brain has internalized regularities associated with terrestrial gravity. An internal model of gravity is thought to arise from the integration of vestibular, visual, proprioceptive and visceral sensory cues. However, it remains unclear whether this internal representation of gravity contributes to the perception of physical object properties. Object weight is determined by the product of its mass and gravitational acceleration. Although previous studies have examined how an object's visual properties, such as its size, shape and texture, influence perceived weight, no study has investigated the effect of altered visual-gravitational information. Here, participants judged the weight of physical objects while they experienced virtual reality environments in which virtual objects accelerated according to either terrestrial gravity (Earth: 9.81 m s‒2) or partial terrestrial gravity (Mars: 3.71 m s‒2). Participants perceived the objects as lighter when viewing Mars gravity relative to Earth gravity. Our results suggest that participants incorporate visual-gravitational information when perceiving object weight, and that the internal model of gravity adapts to altered visually simulated gravitational environments.