  A recent psychology study found that people sometimes reject overly generous
offers from people because they imagine hidden ''phantom costs'' must be part
of the transaction. Phantom costs occur when a person seems overly generous for
no apparent reason. This study aims to explore whether people can imagine
phantom costs when interacting with a robot. To this end, screen or physically
embodied agents (human or robot) offered to people either a cookie or a cookie
+ \$2. Participants were then asked to make a choice whether they would accept
or decline the offer. Results showed that people did perceive phantom costs in
the offer + \$2 conditions when interacting with a human, but also with a
robot, across both embodiment levels, leading to the characteristic behavioral
effect that offering more money made people less likely to accept the offer.
While people were more likely to accept offers from a robot than from a human,
people more often accepted offers from humans when they were physically
compared to screen embodied but were equally likely to accept the offer from a
robot whether it was screen or physically embodied. This suggests that people
can treat robots (and humans) as social agents with hidden intentions and
knowledge, and that this influences their behavior toward them. This provides
not only new insights on how people make decisions when interacting with a
robot but also how robot embodiment impacts HRI research.
