But Bilge Mutlu and colleague's team at Carnegie Mellon University, Pittsburgh, have robots that "leak" non-verbal information through eye movements when interacting with humans. The eyes of a robot may not provide a window into its soul, but they can help humans guess the machine's intentions.
Humans constantly give off non-verbal cues and interpret the signals of others – but without realising it at a conscious level, says Mutlu. The trembling hands of a public speaker betray their nerves even before a word is uttered, while poker players leak subtle signs such as eye flickers or twitches that can be used to spot bluffers.
But when faced with a robot all our interpretive skills are irrelevant. Robots leak no information, so it is virtually impossible to read their intentions, which makes them hard to get along with.