IQ

They are pretty limited and often quite biased.

 

http://www.apa.org/monitor/feb03/intelligent.aspx

http://psychology.about.com/od/intelligence/a/intelligence.htm

Agreed.

Here is a paper I read about the effects of poverty in a child's development. It suggests lower income, lower IQ.

Brief summary: http://onlinelibrary.wiley.com/doi/10.1111/1467-8624.00133/abstract

Article download: http://r.duckduckgo.com/l/?kh=-1&uddg=http%3A%2F%2Fwww.childrenshealthwatch.org%2Fupload%2Fresource%2FDuncan2000.pdf

Now in my opinion I don't think economic status should have anything to do with intelligence, I knew a girl in my 4th grade math class that was so poor she always had holes in her clothes and shoes, she was my best friend, we would read Shakespeare together and act out some of the parts (yeah, in 4th grade, lol). She was a wiz at math too she always had to help me in that area. She loved to read and read everything I think that was the key. The want, the ability, and the drive to read is very important for a child to have.