Imagine having your own humanoid robot. It is great at its job so your floors and windows are gleaming and spotless, but it has an annoying habit of vacuuming the living room when you have a headache, or offering you a meal just as you are drifting off to sleep on the sofa.

If you sometimes have difficulty reading other people's expressions and emotions, imagine how difficult it will be for silicon-brained robots. They will only ever be able to respond to us in an appropriate way if they can understand human moods.

What robots need is kansei. The Japanese term encompasses a raft of emotional notions, including feeling, mood, intuitiveness and sensibility. Without kansei, says Shuji Hashimoto, director of the humanoid robotics centre at Waseda University in Tokyo, the service robots being developed around the world will not be able to acquire the social skills they will need to ...