Look despite the grades, the social skills, and all the BAKA 

incidents, 

when it comes to martial arts Ranma is the most inteligent person on 

earth.  

<ROTFL>  Except for Tarou, Kumon Ryuu, Ryouga, Konatsu, Herb, Kiima...

	My take on it is that everyone else was encouraged to use their inate 
inteligence while they were training.  Ranma was trained by Genma, a total idiot 
who DISCOURAGED Ranma from ever thinking.  Because of this Ranma avoids thinking 
a problem through unless he has no choice in the matter.  Thing is when forced 
to he has outthought just about every opponent he's faced.  So Ranma's opponents 
are guy's of varying inteligence who were trained to fully use that inteligence 
all the time, whereas Ranma is a genius levil intelict who's training prevents 
him from using anything more than a fraction of his brainpower except when 
confronted with extreme necessity.

Uhh...not quite.  Tarou had maybe half an hour to look at it, and the 
reason Ranma figured out what it is is because he is FAMILIAR WITH
MODERN MEDICINE, while Tarou, a nomad from the backwoods of China, 
didn't know what they were even after seeing Rouge buy some.

	Ranma and Tarou are both Martial artists, and thus they should both have 
the experience to see that the difference in Rouge's fighting style was caused 
by back pain.  No knowlege of modern medicine required.  Tarou didn't see it 
despite having longer to see it, Ranma however spotted it right away.