Mice and monkeys show a general intelligence factor much like human IQ
The g factor, the statistical thread linking scores across different mental tests, was first found in people. It now turns up in other animals too, explaining about 47% of the variation in primate problem-solving and 55 to 60% in mice, figures close to the 40 to 50% seen in humans.
Intelligence resists a tidy definition. It has been described as the capacity for abstraction, logic, learning, planning, creativity and problem-solving, or more simply as taking in information, keeping it and using it to adapt. When two dozen leading theorists were asked to define it for a 1995 American Psychological Association report, they produced two dozen different answers. The word comes from Latin intelligere, to comprehend, and medieval scholars used intellectus for understanding; Bacon, Hobbes, Locke and Hume preferred plain understanding, and Hobbes mocked the phrase the understanding understandeth as an absurdity.
In humans, IQ tests were first built early in the 20th century to identify children with intellectual disabilities and later spread to screening immigrants, soldiers and job seekers. The g factor summarises how scores on varied tests tend to rise and fall together. Most psychologists accept that IQ captures some abilities, especially for academic success, while doubting it measures intelligence as a whole, and the scientific consensus is that genes do not explain average IQ gaps between racial groups. Researchers also describe emotional, social and moral forms of intelligence.
Animals cannot sit verbal exams, so researchers probe innovation, habit reversal, social learning and reactions to novelty. Wolfgang Köhler studied apes, Stanley Coren wrote about dogs, and chimpanzees, bonobos such as the language-using Kanzi, dolphins, elephants, parrots, rats and ravens all get attention. Cephalopods are especially revealing because they seem clever while their nervous systems are built along radically different lines from ours. Defining intelligence so it means the same across species, and measuring it fairly, remains the central difficulty.
Plants push the debate further. Some argue they deserve the label because they sense and model their surroundings and reshape their bodies to survive and reproduce, and they can register good and bad experiences and communicate. Critics counter that intelligence involves persistent memories and learning, which would admit machine-learning robots but exclude purely automatic plant responses. The question remains controversial.
Source: Intelligence
