* I might need a name for this adjusted attribute. "Raw Attribute" works for the unadjusted score in the 3-18 range. I could just say "Adjusted Attribute", but that might be confused with bonuses or penalties added to the attribute. Plus, I really would like to find a shorter word.
Why Wisdom or Dexterity? I interpret Wisdom to be an awareness of wrongness, in almost any sense of the word. So, it's danger sense, common sense, and moral sense, all rolled into one. And Dexterity is of course reactio time. You pick the better of the two, since even if characters are so thick that they miss clues to a possible ambush, they still might be sharp enough to adjust quickly to the new situation. Rolling high over Wis/3 or Dex/3 means the character is surprised.
Average raw Wisdom or Dexterity is in the 9 to 12 range, which makes the Attribute/3 score either 3 or 4. There's a good chance that at least one of the two scores will adjust to a 4, so the typical adventurer will be surprised on a 5 or 6 on a d6 roll. This is equivalent to the original surprise chance of 1 or 2 in 6. Characters with sharp senses might get a +1 on their surprise target, only being surprised on a 6. Other factors that might give a +1 bonus:
- familiar with the area
- multi-headed/eyes in back of head
- ground cover is noisy (lots of dried leaves or twigs, for example)
- low, bright light behind other group produces long shadows
- busy with another task
- dulled senses
I'll have to cover how surprise relates to thievery in another post.