I've been practicing on an Ear Trainer program for my iPhone, and I've noticed a distinct pattern. The way the program works you tell it what intervals/scales/chords you want to practice, and it'll play two variants of it and have you identify one of them. For example, if I'm practicing seconds then it'll choose a random root note, then play a minor and a major second from that root and have me identify the major second.
What I've noticed through this practice is that while I'm usually pretty consistent at identifying the intervals when ascending, even when I'm confident about my responses I seem to do little better than just random guessing when the intervals are played descending.
On the one hand, this helps explain why I've always had trouble tuning by ear, on the other hand I'm wondering why it's so hard to tell intervals I otherwise know cold when they're descending instead of ascending. Can anyone offer some insight into this?