Poll: the sum(7,9)

[Mark Swindell]

I've got a question I'd be interested in hearing from as many of the 
list as care to respond.

It's this:  How do you mentally process simple addition/subtraction 
facts?  What actually happens in your brain to elicit 16 when you hear 
7+9? (for example)

Why do I ask?
Three adults I asked today:
#1: I visually see 7 fingers and 9 fingers and move one finger from the 
7 to the 9 to make 10, and 10 and 6 are 16.  But it happens 
instantaneously. (visual concrete... strategic)
#2: I simply visualize the 7 and the 9 and "see" a 16 as the missing 
third party. (visual symbolic... pattern,grouping)
#3: I roll the tape from my parochial school days: "7 plus 9 is 16."  
(Actually a Spanish tape, though the person has spoken high-level 
English for 30 years.)(auditory... linear)

I ask because I wonder what the implication for having young children 
memorize their addition/subtraction facts?  Is it solely a product of 
the teaching, or that combined with a process of the individual mind 
that works a predisposed way to make sense on its own terms?   What is 
the most efficient way to store this data?  :)

The results may end up in a Rev product of some kind... who knows?

Thanks,
Mark