I was just talking to my friend about this 3 years ago. Basically, all these tests (except iq, which probably doesn't mean much) CAN be studied for.
I studied 6 months for SAT and got 1590. At my high school, everyone was crazy about their SAT.
In college, I was too busy screwing around and being lazy to study more than 6 weeks for MCAT, and I got a 35: 10V,13P,12B,R
Well, I have friend1 who scored 1580 on his SAT (studied hard), and studied hard for MCAT. He ended up getting 39 on his mcat. In med school, he relaxed and did not study as hard for boards to get a 245 (he's a real smart kid either way).
But get this ok, friend1 did not study for the SATs in high school, he didn't even realize he was supposed to. He scored around 1200-1300. In college, he studied MCATs with me and we both studied hard but only for 1 month and got a 34. But then he takes his board scores which he said he studied like there was no tommorow and scored 245, tying friend1 who had 39 on his MCAT.
So you see, the amount of effort you put in will make the greatest difference. Also, don't waste you effort with ****ty books, go with big names like kaplan or princeton review or berkeley review when studying. don't use like arco's or something like that.
one last note, even when talking to my attendings i try not to mention specific scores because i don't want to distance myself from others, instead i want to encourage. if you just get double digits in each category on mcats, and are well-rounded, med schools will want you. There is no medical school that will take you solely on the basis of test scores. I have a friend who got 40 on his mcat but was rejected from all UC's b/c his essay and activities showed no effort. Only if you score 43 or higher will schools consider taking you if you have zero activities.