Figure 1.
The physical and visual properties of the stimuli.
(a) The large and small metal and polystyrene cubes, all adjusted to weigh 700 g and (b) graphical representation of the difference in the size-weight relationship between high density and low density materials.
Figure 2.
The size-weight illusion as a function of object material.
Participants’ reported perceptions of heaviness for the large and small metal and polystyrene cubes. The lower panels show the z-normalized ratings for all the cubes on each trial. These data are fit with 4th order polynomials to indicate the mean trends (no statistics were performed on these curves). The top panels show the average magnitude of the illusion (large cube rating subtracted from small cube rating) over the course of the entire experiment. Error bars indicate between-subject standard error of the mean.
Figure 3.
The effects of object size and material on the fingertip forces.
The peak grip force rate (GFR – left panels), peak load force rate (LFR – middle panels), and load force at the first peak in load force rate (LF1st – right panels) recorded during lifts of the large and small cubes made from the different materials. The lower panels show the forces for all the cubes on each trial. These data are fit with 4th order polynomials to indicate the mean trends (no statistics were performed on these curves). The top panels show the average magnitude of the size-based errors (force to lift small cube subtracted from force to lift large cube) over the course of the entire experiment. Error bars indicate between-subject standard error of the mean.