Haha, closely linked my ass dude, that graph isnt comparing shit. The ASVAB is a multiple choice assessment test, not an IQ test. The Ravens test is a nonverbal multiple choice test, and while you can infer IQ from it, its far from the most trusted of IQ tests. Gee, looks like when you hand a person a standardized test, they do about the same on it! And the correlation isnt "close" at all, use your eyes and look at the fucking deviation. Sure, you can get an estimate, but I doubt anyone would accept a IQ score converted from a SAT as legitimate.
The entirety of what I have to say of that next comment you made depends on the validity of the article you post (The one here seems to be about IQ and motivaiton, not head size...). But from all of the studies I've seen and read, brain size or brain ratio has little to no effect on the individual level. Species level, yes, my head being .05cm larger than hers = no.
As for IQ's and SAT's being good tests that accurately measure cognitive ability; Bull. Shit. Assessment tests are inherently flawed, both by their format and by their creators. I had a student who has failing in school and (hate to say it) kinda a loser, but had the highest scores across the board out of all the students in my SAT class. Some people are just good at unraveling the test and picking up on the relationship of answers and questions. As a teacher, I can look at a reading passages questions and answers and get most right without reading the passage. A lot can be inferred from the way the test is made, if you understand and know its subtleties, which some people can inherently do better than others. Finally, the SAT's and IQ's are terrible tests because they're made by rich white guys for rich white guys. Look who the SAT caters most to:
This is data from a 1997 SAT, 1 million test takers average scores. There is bias, and this bias confounds the score and assessment. The entire idea of having a test or standardized analytical assessment for ones intelligence is somewhat ridiculous. Intelligence can be any number of things, such as tracking an animal, knowing how to fix a car, speed reading, logic and reasoning, ability to recall the 27th digit of pi... theres an infinite amount you could test for, and just because someone is good at one or many 'skills' doesnt mean they are a genius - you could (for an extreme example) have just had a lucky savant that knew only your questions. I'm sure people out there are stupid enough to trust numbers that we so ungracefully bestow on someones 'ability', but speaking from a SAT tutor, I've seen a lot of dumb kids get really high scores and lots of smart kids completely stumped by a assessment test. Ones intelligence will never be able to be truly assessed and assigned a nice neat number.
