I can relate to that a little bit. More often than not, I don't truly "care" about what people are telling me, so I have a hard time mustering up a genuine reaction or response.For me, it's not that I'm not showing interest. It's more of a problem of "displaying" interest. Many like to know they have your undivided attention and/or expect a reply when none is nessecary.
Sometimes I would play into what people expect, but then I feel fake.
And I hate when I'm situations where people are saying things and you know they want some type of response or acknowledgment, but their comments really don't lend themselves to a natural or meaningful response. :/