Watson’s hand is pretty fast in terms of raw speed — it takes somewhere between five and ten milliseconds for Watson to activate the buzzer once it decides to answer. This delay is affected by the speed of the solenoid and other small, sometimes hard-to-pin-down delays inherent in the software stack.
http://www.kurzweilai.net/the-buzzer-factor-did-watson-have-...
I wonder if the human decision-to-buzzer time is much slower?