Training can improve fluid inteligence.

Most IQ tests attempt to measure two types of intelligence–crystallized and fluid intelligence. Crystallized intelligence draws on existing skills, knowledge and experiences to solve problems by accessing information from long-term memory.

Fluid intelligence, on the other hand, draws on the ability to understand relationships between various concepts, independent of any previous knowledge or skills, to solve new problems. The research shows that this part of intelligence can be improved through memory training.

Why does the training can improve our fluid intelligence?
The authors find some features of fluid intelligence relevant to the ability to solve new tasks.
This ability includes ignoring irrelevant items, monitoring ongoing performance, managing two tasks simultaneously and connecting related items to one another in space and time. The more times you are faced with new problems the stronger the above aspects you have.

The authors don’t know how long the improvement will last after giving up training.

Read more:
http://www.nytimes.com/2008/04/29/health/research/29brai.html