Table 3. Factor loadings of each variable as determined by the Principal Component Analysis.

Variable	Physical interaction determinant	Behavioral determinant
pleasantness	−0.88	0.15
fN	−0.04	0.77
β	0.94	0.11
α	−0.77	−0.41
μ	0.81	−0.33
v	0.01	0.82

pleasantness: materials' pleasantness levels; f_N: normal force component; β: the magnitude of friction-induced vibrations in the spatial domain; α: decay coefficient of friction-induced vibrations in the spatial domain; μ: dynamic coefficient of friction; v: exploration velocity.