The ability to detect chords is also something that is facilitated further if you have good relative pitch to begin with. It is also something, that the more you do it, the finer your "instincts" become.

When I was actively involved with bands professionally over the years, my job usually involved doing the arrangements or "lifts" for the band. It got to a point where once I had a lock on a given recording, I could clearly hear and know what the chord changes were to a given song. But it drove me nuts when I'd go out and listen to other cover bands, and hear wrong chord changes when they'd perform. If I knew the band leader I'd point it out to him...and more often than not they'd say "Thanks. You're right. I wasn't sure of this or that chord." Then again, there have been many a major argument and screaming match had in rehearsals where two people debate what a given chord is, with both sides adamantly claiming they're right and the other is wrong. (I seem to remember listening years ago to outakes from a Trogs recording session, where the engineer had let the tape roll, and two guys in the band were going ballistic towards each other over how the song they were trying to record, went.)

But definitely lifting chords is akin to exercising. The more you do it, the easier it becomes. Of course, the more extensive your existing knowledge of chords and their respective sounds are, the easier this is as well.