[6] Similar illusions occurs with differences in material and colour: metal containers feel lighter than wooden containers of the same size and mass,[7] and darker objects feel heavier than brighter objects of the same size and mass.
[14] An early explanation of these illusions was that people judge the weight of an object from its appearance and then lift it with a pre-determined force.
[15] This hypothesis was disproved by an experiment in which two objects of the same mass, same cross section, but different height were placed on observers' supported hands, and produced a passive size–weight illusion.
[16] Recent studies have also shown that the lifting force quickly adapts to the true mass of the objects, but the size–weight illusion remains.
[17][18][19] The illusion therefore cannot be explained by the manner of lifting, and must be due to some perceptual rescaling based on prior expectations.