What is intelligence?The concept of intelligence is difficult to describe. One way, is to describe intelligence in three levels of analysis:Some see intelligence as one factor called general intelligence, g. General intelligence are cognitive processes influencing the ability to think and learn on all intellectual tasks.There are also good arguments for intelligence to consist of two types of intelligence. Namely: fluid intelligence and crystallized intelligence. Fluid intelligence is the ability to solve new problems at a certain moment, for example by drawing conclusions and understanding relationships between concepts that have never been encountered before. Fluent intelligence usually peaks in early adulthood and then slowly decreases. Crystallized intelligence is the actual knowledge about the world. Crystallized intelligence starts early in life and continues to multiply. Thurstone divides intelligence in a complex way into seven skills. These are the so-called seven primary mental abilities crucial for intelligence: word fluency, verbal meaning, reasoning, spatial visualization, numbering,rote memory and perceptual speed. The division of intelligence into seven abilities equals the distinction between fluid and crystallized intelligence. Some scores on certain abilites correlate more with each other than with scores of other abilites.The third view sees many different processes involved in intelligence. This leads to more specification of processes in intellectual behavior than the other two levels.The perspectives can be brought together. According to Carroll, there is a model for intelligence: the three-stratum theory of intelligence. This model contains general intelligence in the top layer of the hierarchy, then several moderately general abilities in the middle layer, and at the bottom layer a large number of specific processes. In short: all three levels are necessary to understand and measure intelligence.How can...