How did Stephen Hawking talk though a computer when he couldn’t move?

Question

I read that Stephen Hawking used some kind of infrared sensor on his glasses that sensed his cheek muscle moving which would then speak though a voice synthesizer, but how did that work? How would the computer know which word he was trying to type/speak if he could only move his cheek muscle?

In: 4

Answer 1

He was confined to a wheel chair, but that doesn’t mean he couldn’t move at all. He used his thumb to move a joystick and he blinked to select words.