automaton:
(plural: automatons or automata)
a person who acts or reacts without feelings or thought as if he/she were a machine, i.e. just reacts mechanically,
an automaton (standing) listening to the boss without any reaction
Consumer culture, i.e. buying and spending money of consumers, turns many intelligent people consumer automatons. (from sentence.yourdictionary.com)
Mary is an automaton; nothing in this world excites her
My assistant is such an automaton that he does not even bother to show his feelings when he does not like my ideas; he just follows my instructions!

