Fluid intelligence is tied to biology. It is defined as our
"on-the-spot reasoning ability, a skill not basically dependant on our
experience."
Brain Workshop - a Dual N-Back game

Brain Workshop is a free open-source version of the dual n-back brain
training exercise. A recent study published in PNAS, an important
scientific journal, shows that a memory task called dual n-back
improves working memory (short term memory) and fluid intelligence.
These findings are important because fluid intelligence was previously
thought to be unchangeable.
Introduction - Download - Tutorial - Details & Options
Similar Minds

SimilarMinds.com is a resource for personality tests and personality psychology. All the tests at SimilarMinds.com are developed based on scientific measures used to ensure test validity. You can test yourself in Visual Pattern Fluid Intelligence Test
IQTest.dk

Welcome to IQtest.dk. This test is developed with the aim of
measuring your Intelligence Quotient (IQ)