The Effect of Human-Likeliness in French Robot-Directed Speech: A Study of Speech Rate and Fluency.

Robot-directed speech refers to speech to a robotic device, ranging from small home smart speakers to full-size humanoid robots. Studies have investigated the phonetic and linguistic properties of this type of speech or the effect of anthropomorphism of the devices on the social aspect of interaction. However, none have investigated the effect of the device’s human-likeliness on linguistic realizations. This preliminary study proposes to fill this gap by investigating one phonetic parameter (speech rate) and one linguistic parameter (use of filled pauses) in speech directed at a home speaker vs a humanoid robot vs a human. The data from 71 native speakers of French indicate that human-directed speech shows longer utterances at a faster speech rate and more filled pauses than speech directed at a home speaker and a robot. Speaker- and robot-directed speech is significantly different from human-directed speech, but not from each other, indicating a unique device-directed type of speech.