Size-Weight Illusion

Using fMRI, we show that the perception of object weight and the prediction of force required for lifting are supported by distinct neural circuits — providing key evidence for separate visuomotor and perceptual streams.

When lifting objects with one hand, the brain builds internal models predicting the force required. This study shows these predictive grip force models transfer across hands independently of how heavy the object feels — dissociating motor prediction from perceptual weight estimates.