Perceptual data, showing the three axes of the Principal Component Analysis (PCA) per participant and per physical force magnitude.
Black: first component, blue: second component, red: third component. Top (a) and side view (b), with each vector corresponding to one participant. Top (c) and side view (d), with each vector corresponding to one physical force magnitude, while the data were averaged over participants. The first component is considerably larger than the second and third component, resulting in eccentricities (i.e. the ratio between the eigenvalues of the third and first component of the PCA) that were well below 1. The orientation and size of the components are consistent over participants and physical force magnitudes. Together, this illustrates the consistent anisotropy in force magnitude perception.