Intelligence is defined as the ability to learn, reason, and solve problems. There are various approaches to defining and assessing intelligence, including psychometric testing which measures cognitive abilities, and multiple intelligences theories which propose separate abilities. Intelligence tests measure abilities like verbal, abstract, and quantitative reasoning. The Stanford-Binet Intelligence Scale is a widely-used and reliable test that assesses intelligence through subscales in these cognitive areas from childhood through adulthood. Fluid intelligence refers to abstract reasoning ability while crystallized intelligence involves accumulated knowledge and skills over life experiences. Learning is defined as a relatively permanent change in behavior resulting from experience.