Scientists at the University of California have unveiled a "hyper-realistic" robot that has taught itself to smile and frown.
The robot, whose face is crafted in the likeness of famous physicist Albert Einstein, has about 30 facial muscles, each moved by a tiny servo motor connected to the muscle by a string.
Computer science PhD student Tingfan Wu said the robot learnt to make different facial expressions through a process of self-guided machine learning.
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