Figure 1: Experimental setting, variables, and spatial location
control.
a) Experimental setting: the participants sat facing a computer
monitor with their chin and forehead on a headrest to ensure stability
and reduce any unintentional movement during pupil recording. They were
invited to place their left arm on the table with their palm facing
down. The researcher standing on the left side of the experimental
subject performed different types of touch on either the dorsal side of
the hand or the dorsal side of the forearm of the participant.b) Experimental variables: participants received a CT-optimal
touch stroke velocity (a dynamic stroking with a speed of 3 cm/s) and
CT-suboptimal touch velocity (a static touch). The nature of the
stroking effector promoting the touch was either a Human hand or an
Artificial hand.