Brain

I don't know, but regarding the fact the my cousin called his friend one time "a subject with a green-pea brain", there might as well be...

Anyway, on a more serious point, i'd advise you to take a look at this:

Cerebrum

Function:
Determines Intelligence
Personality
Interpretation of Sensory Impulses
Motor Function
Planning and Organization
Touch Sensation

Location:
The cerebrum is located in the anterior portion of the forebrain. It is divided into two hemispheres that are connected by the corpus callosum. The hemispheres are divided into lobes: frontal, parietal, temporal, occipital and the insula.

With other words, there might be something different about this part of the brain/brain cells/specifically their gene information, or God knows what, that determines the intelligence of a person.

I've also heard that having a larger corpus callosum (the part that connects the hemispheres) affects your thinking. Some site somewhere claims that Einstein was possibly a genius because he had a larger corpus callosum than the average person. The physical size of part of the cerebrum may indicate intelligence.

There are certainly differences in size between people, but they aren't coorelative of inteliggence, On the other hand, There is a certain correlation between the body:brain ratio of a certain species to its normal intelligence. In humans, there are other aspects, such as the number of connections between the neurons. its seems that the diiference will be not in the number of the things, but in the way that they are connected. since we do not know the corealtion between the connections and the thoughts of a person, though we do know the correlation of some of the functions, we can maybe know who we will be better in certain functions, such as verbal, spacial memory, etc.

Thought you might find this of interest,

http://www.lrainc.com/swtaboo/stalkers/em_intmy.html