Full Idea
In functionalism, it is very hard to see how there could be a single physical characterization of the inputs and outputs of all and only creatures with mentality.
Gist of Idea
In functionalism, what are the special inputs and outputs of conscious creatures?
Source
Ned Block (Troubles with Functionalism [1978], p. 87)
Book Reference
'The Philosophy of Mind', ed/tr. Beakley,B /Ludlow P [MIT 1992], p.87
A Reaction
It would be theoretically possible if the only way to achieve mentality was to have a particular pattern of inputs and outputs. I don't think, though, that 'mentality' is an all-or-nothing concept.