Figure 2: Spatial location, pupil dilation responses and
subjective rating
a) Spatial location control: heatmaps show the gaze position
during a 10-second grey square (stimulus) in which the participant
received a tactile stimulation. None of the four heat maps (depicting
the 4 experimental conditions) showed any meaningful eye movements
deviation from the stimulus presented on the center of the screen.b) Bar plot shows the Z-scored mean pupil size values
normalized to baseline during Dynamic and Static touch promoted by a
Human hand and Artificial hand. The inset on the left shows pupil
dilation traces aligned to the time of Dynamic touch promoted by a Human
hand (pink) and Artificial hand (yellow). The inset on the right shows
pupil dilation traces aligned to the time of Static touch promoted by a
Human hand (purple) and Artificial hand (light blue). The shaded traces
represent ± s.e.m. centered around the mean. Vertical dotted grey line
indicates the beginning of touch (10-second duration). The grey shaded
area represents the analyzed epoch. c) Scatter plot shows the
supralinearity effect by contrasting participants’ pupil size in
Dynamic_Human condition alone (y-axis) against Dynamic_Artificial plus
Static_Human conditions summed together (x-axis). d) Violin
plots show the mean subjective ratings reported by participants in the
four conditions: Dynamic touch promoted by a Human hand (pink), Dynamic
touch promoted by an Artificial hand (yellow), Static touch promoted by
a Human hand (purple), and Static touch promoted by an Artificial hand
(light blue). Data points overlaid on top show each subject. In black it
is depicted the mean and in red the median. ***, p <
0.001; **, p < 0.01; *, p < 0.05;
n.s., not significant.