A 24-year-old graduate student from Tokyo University has created the first robot "that can feel fear" - mechanical buttocks that quiver when you spank them or clenches with "pleasure" when you stroke them, Britain's Daily Mail newspaper reported.
"Spank the buttocks, and they quiver. Stroke them and they clench, using artificial muscles under their silicone skin. A built-in microphone detects slaps," the daily said.
Takahashi, a student of Electro-Communication, said the mechanical buttocks are one of the first robots that can convey emotions like fear, joy and relaxation.
The inventor hopes to use the proto-type technology to develop responses that can be applied to other parts of a robot's body, in particular the face.
Takahashi programmed his creation, called "SHIRI" or "butt" in Japanese, to respond with different emotions to different human touches.
He said he decided to develop his technology with a rear end because a bottom's movements are large and make it easier to convey emotion, the daily said.
"Fear is a very human, very living, emotion. So it's expressed with force, with a spank," he said.
The silicon-coated bottom responds to a hit with quivering. A slow wobble is its default state, the sign for relaxation, while a gentle stroke brings about clenches that Takahashi said mean pleasure.
The robot butt contains a skin of silicone over a foam structure, under which lie artificial muscles that be inflated or deflated to simulate different moods.
Also tucked inside is a microphone that detects when the cheeks are being touched, rubbed or slapped and responds accordingly.