How do we decide how heavy an object is?

One might think that heaviness perception is based on estimates of force: a combination of afferent (tactile, proprioceptive) and efferent informations. However, forces are not all that matter, as the perceived weight can be affected by visual information about the size (size-weight illusion). This illusion is frequently interpreted in terms of predictive coding, being induced by a contrast between expected heaviness and sensory information.

In this talk, I will answer three questions related to heaviness perception and the size-weight illusion:

• Is it the force to counteract gravity (weight), or to accelerate the object (inertial mass) that determines our percept?

• Is the size-weight illusion based on size information providing an estimate of the volume of material?

• Is the size-weight illusion based on size information setting expectations, or does size act on-line?