The concept of intelligence is not generally considered controversial. However, it is an idea that can be very tricky to define. Different psychologists have proposed several different theories to answer the question "What is intelligence?" ” and, although they overlap, there is no universally accepted definition. Additionally, because it is difficult to measure intelligence quantitatively, the connotation of the word "intelligence" must be taken into account in the definition. A possible definition of intelligence is "the ability to excel in a certain area that involves rational thinking." As excellence is subjective, it is important to note that this definition requires the use of a comparison. For example, an intelligent person is someone who excels above the norm in a certain subject or area involving rational thinking. A dolphin is very intelligent in the realm of other animals, but a specific dolphin might not be intelligent compared to other dolphins. The question of how to define intelligence is not new. Psychologists have worked for years to determine a way to categorize, measure and define intelligence, and several theories have stood out. The first widely known theory was developed by British psychologist Charles Spearman, born in 1863. After conducting tests measuring subjects' mental abilities, "he concluded that intelligence is a general cognitive ability that can be measured and expressed digitally” (Cherry). . His theory is known as general intelligence. Dictionary.com's definitions of intelligence include "the capacity for learning, reasoning, understanding, and similar forms of mental activity; the ability to grasp truths, relationships, facts, etc. .... middle of paper..... .00 signs in sign language and refers to itself as "orangutan person", while other, less sophisticated orangutans are given the label "orange dog » (Antonetta, 2005). Research should be conducted to test the cognitive abilities of many more monkeys. org/index.php/articles/article/6474/http://www.orionmagazine.org/index.php/articles/article/152/http:// www.aboutintelligence.co.uk/the-theory-multiple-intelligences.htmlhttp://psychology.about.com/od/cognitivepsychology/p/intelligence.htmdictionary.comhttp://psychology.about.com/od/psychologicaltesting/ a/int-history.htm