  Inner Speech is an essential but also elusive human psychological process
which refers to an everyday covert internal conversation with oneself. We argue
that programming a robot with an overt self-talk system, which simulates human
inner speech, might enhance human trust by improving robot transparency and
anthropomorphism. For this reasons, this work aims to investigate if robot's
inner speech, here intended as overt self-talk, affects human trust and
anthropomorphism when human and robot cooperate. A group of participants was
engaged in collaboration with the robot. During cooperation, the robot talks to
itself. To evaluate if the robot's inner speech influences human trust, two
questionnaires were administered to each participant before (pre-test) and
after (post-test) the cooperative session with the robot. Preliminary results
evidenced differences between the answers of participants in the pre-test and
post-test assessment, suggesting that robot's inner speech influences human
trust. Indeed, participant's levels of trust and perception of robot
anthropomorphic features increase after the experimental interaction with the
robot.
