In an experiment we manipulated a robot's voice in two ways: First, we varied robot gender; second, we equipped the robot with a human-like or a robot-like synthesized voice. Moreover, we took into account user gender and tested effects of these factors on human-robot acceptance, psychological closeness and psychological anthropomorphism. When participants formed an impression of a same-gender robot, the robot was perceived more positively. Participants also felt more psychological closeness to the same-gender robot. Similarly, the same-gender robot was anthropomorphized more strongly, but only when it utilized a human-like voice. Results indicate that a projection mechanism could underlie these effects.

Recent research has shown that anthropomorphism represents a means to facilitate HRI. Under which conditions do people anthropomorphize robots and other nonhuman agents? This research question was investigated in an experiment that manipulated participants' anticipation of a prospective human-robot interaction (HRI) with a robot whose behavior was characterized by either low or high predictability. We examined effects of these factors on perceptions of anthropomorphism and acceptance of the robot. Innovatively, the present research demonstrates that anticipation of HRI with an unpredictable agent increased anthropomorphic inferences and acceptance of the robot. Implications for future research on psychological determinants of anthropomorphism are discussed.