Mixing words and numbers in a sentence?

["Geoff Hart" <geoff-h -at- mtl -dot- feric -dot- ca>]

John Posada queried the sentence: "Note: You can change the 
default display from 4 images to 9 or 16 images by selecting 
"Image Display Options" from the menu bar."  <<One of the 
developers is wearing his tech writer hat and is mumbling that the 
numbers 4 and 9 should be written as words>>

Although that's not a bad rule in general writing, it doesn't 
accomodate one fairly basic feature of human perception: the mind 
processes numerals, words (including words for numerals), and 
graphics in different manners. In effect, the mind changes over to a 
new mode of processing (a new "context") to process each 
different type of information it encounters, then changes back 
again. (Wish I could remember where I read about this... a psych 
textbook, if memory serves, but I don't remember which one. Any 
cognitive scientists out there who can provide details in the form of 
a good reference?)

So keeping the numbers all in the same form (numerals) minimizes 
context switching and makes for more efficient processing of the 
information. How significant this repeated context switching 
actually is in terms of reading speed and comprehension hasn't, to 
my knowledge, been demonstrated through research, though I don't 
keep up on these things anymore and probably missed something. 
But in all likelihood, using both numerals and words probably 
represents at least a slight "friction" on reading, and why add any 
friction to reading? That suggests sticking with the numerals 
throughout.


--Geoff Hart @8^{)}  geoff-h -at- mtl -dot- feric -dot- ca  (Pointe-Claire, Quebec)
"If you can't explain it to an 8-year-old, you don't understand it"--Albert Einstein