Is relative brain size
really proxy for Intelligence?

Zoology / 6 min read / 9 May 2021

Lazy Science Reader,

Our thinking machine, one of the most tremendous and amazing results of Evolution. The abilities that make us humans one among the foremost intelligent species are our Cognition power, Curiosity, and Reasoning ability. We used our brains to form methods to measure our intelligence which is named "IQ", coined by the psychologist William Stern for the German term Intelligenzquotient, his term for a scoring method for intelligence tests at the University of Breslau he advocated during a 1912 book.

Encephalization Quotient has been used as a proxy for intelligence and thus as a possible way of comparing the intelligence of various species. For this purpose, it is a more refined measurement than the raw brain-to-body mass ratio, because it takes into account allometric effects. Expressed as a formula, the connection has been developed for mammals and may not yield relevant results when applied outside this group.

Brain size relative to body size which was long considered to be a proxy for intelligence and thus as a possible way of comparing the intelligence of various species is now somewhat proven wrong as shown by the research work published in Science Advances.

The animals like humans, dolphins, and elephants, have big brains compared to their body size. These reached their proportions in several ways. Elephants increased in body size but increased even more in brain size. Dolphins, on the other hand, generally decreased their body size while increasing brain size. Great apes showed a large variety of body sizes, with a general trend towards increases in brain and body size. Ancestral hominins, which represent the human line, showed a relative decrease in body size and increase in brain size compared to great apes.

The very fashionable long-standing belief that relative brain size is usually equivocated with intelligence has been overturned." says Kamran Safi, an enquiry scientist at the Planck Institute of Animal Behavior and senior author on the study. They also concluded on the very fact that relatively big brains are often the results of the decrease in body size thanks to global climate change or change within the habitat of the respective animals. Their study also showed us that the foremost changes in relative brain size were mostly after mass extinctions.

The different animals find suitable conditions and become isolated from one another, they split, regenerating a variety of the range that was exhausted by the mass extinction. The results of these processes are that mass extinctions tend to be followed by periods of rapid diversification and radiation. this might explain the very fact that's covered within the previous paragraph. Thus with every ending comes a replacement beginning.

Fun Fact

Encephalization quotient (EQ) may be a relative brain size measure that's defined because the ratio between observed to predicted brain mass for an animal of a given size, supported nonlinear regression on a variety of reference species.