Figure 4. Heaviness ratings (A) and peak arm acceleration (B) for the five objects tested in zero g, one g, and 1.8 g (mean ± SE of four trials with 12 subjects).

A size-mass illusion was present at all gravity levels, as shown by the smaller heaviness ratings for the taller objects compared to the reference cube. The arm acceleration varied as a function of the gravity level, but it was not different between the five objects.