Speed/Sneak: This is probably the easiest. You can't run and still be quiet and stealthy at the same time.
Speed/Evade: If you'll try to hide while running, you will most probably be unsuccessful.
Fight/Will: It's difficult to be convincing when you're aggresive.
Combat/Horror: If you want to damage a monster more effectively, you need to get closer to it. However, the closer you are, the more frightening the monster seems.
Lore/Luck: When you think deeply, it's easy to not pay attention to your surroundings and, if do try your best to pay attention to your surroundings, thinking clearly is hard.
Spell/Luck: It's difficult to concentrate on both spellcasting and your surroundings at the same time.
You are welcome to discuss with my reasonings. Agree? disagree?