4 February

This is called the size-weight illusion, or Charpentier’s illusion, which I re-discovered accidentally in the kitchen one morning. There are no useful explanations for it. Wikipedia has a nice summary of how all the most obvious explanations fail. “The illusion also occurs when the objects are not lifted against gravity, but accelerated horizontally, so it should be called a size-mass illusion. Similar illusions occurs with differences in material and colour: metal containers feel lighter than wooden containers of the same size and mass, and darker objects feel heavier than brighter objects of the same size and mass. These illusions have all been described as contrast with the expected weight, although the size-weight illusion occurs independent of visual estimates of the volume of material and the illusion does not depend on expectations, but occurs also if visual size information is only provided while already lifting.”