Speech from intelligent "cognitive agents" can vary along a machine-to-human spectrum, from very machine-like to very human-like [3,4]. Effective interaction with such agents may depend on whether they are trusted by human users. This study investigated properties of machine-like speech along a machine-to-human spectrum in order to identify those associated with higher trust. We first examined whether flanging (time delay) and pitch contour could be used to map a machine-to-human speech spectrum. We found that lower pitch range and greater time delay generated more machine-like speech. Subsequently we examined perceived trust levels for different sounds along the spectrum. We found that human-speech had higher ratings of trust than machine-like speech. Finally, we used the behavioral TNO Trust Task (T 3 ) to examine trust and compliance levels with cognitive agents speaking in different voices. The results confirmed that participants complied with and trusted agents with human speech more than agents with machine-like speech.

No abstract