I have experienced several times in the past two days when I probably should have responded to something weighty that people have told me (I can generally fake sincerity quite well in these cases, finish up with the "caring thing" and get them away from me more quickly), but I simply looked at them blankly and did not make a sound, nor a change in my face.
I just sat there looking at them with no expression until they went away. I had heard what was said, but I could not find a way inside myself to make any of it matter to the rest of what I was thinking.
*starts to shrug, decides that it would be more effort than needed*