From the January 5-6, 2013 Wall Street Journal "Week in Ideas" by Dan Akst:
"When it comes to learning math, intelligence counts at the outset. But after that, it's a matter of motivation and study skills.
"That's the result of a German study of 3, 530 students in grades five through 10. Researchers examined six years of data with an eye toward establishing the effect of IQ, motivation and study skills on growth in math achievement.
"Intelligence, it turned out, wasn't a factor in this growth. And rote learning strategies actually did more harm than good. But feelings of control, high motivation and study skills that involved explaining a summarizing math and connecting it to other material did predict greater achievement. What it takes to learn math, the researchers said, isn't just innate; it can be fostered."
Summary of the research from: "Predicting Long-term Growth in Students' Mathematics Achievement: The Unique Contributions of Motivation and Cognitive Strategies," Kou Murayama, Reinhard Pekrun, Rudolf vom Hofe and Stephanie Lichtenfeld, Child Development (Dec. 20)
Notice that explaining and summarizing and connecting the math to other material was very important. To me, that means verbally conceptualizing the math and integrating it with other knowledge about the world - which tends to be motivational because it enables the learning to know how to use the math.