I think this exchange from Legacy spells it out pretty well.
ISHARA
But you don't have feelings, do
you?
DATA
Not as such. However, perhaps
even among humans, friendship is
sometimes less an emotional
response, and more a sense of
familiarity.
ISHARA
(understanding)
You can become used to someone.
DATA
Exactly. As I experience certain
sensory input patterns, my mental
pathways become accustomed to
them. The inputs eventually are
anticipated. And even "missed"
when absent. When something once
expected is no longer there.
As far as Data 'brushing it off' in regards to Picard, I believe he was simply setting it aside until they got to the bottom of things. Data has show a 'duty first' tendency in the past. Take Redemption part II when he is in command of the Sutherland. Only when he succeeds in outing the Romulans does he then order the phasers to be taken off line and the radiaton clean up to begin. He fully understood what the priorities were.