I'm (finally) reading David Huron's Sweet Anticipation: Music and the Psychology of Expectation. In fact, last night I was reading Chapter Seven out loud for Weasley, to help him calm down in his new crate. He apparently finds mental representations of pitch to be very soothing.
One section that struck me was David's debate about the perception of intervals. He thinks that he doesn't perceive the actual intervals, but rather hears the separate notes as scale degrees, which he can then use to identify the interval. I don't have the book with me right now, I'll add the relevant quote when I'm home later. But it is basically this: 1) hear two notes, 2) recognize that they sound like the beginning of "Here Comes the Bride," 3) therefore associating the second note as tonic 'Do' and the first note as 'Sol,' 4) identify the interval between Sol and Do as a Perfect Fourth. Many people would skip step 3 as a conscious part of their process, but it would still be a lower level association that helps them recognize the melody in the first place. Now, here is my issue. David says that following this process is identifying separate notes, and then figuring out the relationship (the interval), much like people with AP. But I don't see how one can identify the second note as Do without hearing the relationship between the two notes. I agree that consciously hearing a Perfect Fourth and hearing Sol - Do are different processes, but both still rely upon the relationship between the notes. This contrasts with the AP perception, which would be 1) hear two notes, 2) label the first note as B3, 3) label the second note as E4, 4) identify the interval between B3 and E4 as a Perfect Fourth. The two notes are given labels that do not depend upon the other note, whereas identifying one note as Do is to place both notes in a tonal context.