When you use this hands-on exhibit…you’ll explore two different weight illusions by lifting and comparing the weight of different shapes. One pair of shapes shows the texture-weight illusion, while the other pair of shapes shows the size-weight illusion.
Have you ever picked up a large box, without realising that it was empty, and almost flung the box into the air?
If you did, your brain probably assumed the box would be heavy, so you primed your muscles to use more force than you actually needed.
The size-weight illusion gives you the impression that a smaller shape (or object) feels heavier than a larger shape, even though the shapes are the same mass.
When two objects are the same mass, but one is larger than the other, your vision unconsciously primes your muscles to lift the larger object with more force or tension compared to the smaller object.
Because the large object needs less muscle tension than you unconsciously expected, the larger object feels unexpectedly light.
Even though you’re getting ‘bottom up’ signals from your muscles that the shapes weigh the same, you still experience the illusion that the smaller shape is heavier.
This size-weight illusion is also known as the Charpentier-Koseleff, illusion.
If you close your eyes and lift the small and large objects at the same time, the illusion of the smaller object feeling heavier seems to disappear.
Some people find the smooth shape feels a little heavier than the textured shape, because they need to use a stronger grip to lift the smooth shape, which gives the illusion that it feels heavier.