What is an encephalization quotient?

The encephalization quotient (EQ) is a measure of brain size relative to the body size of an animal. It is calculated by comparing the actual brain mass of an animal to the expected brain mass for an animal of that size, based on the average relationship between brain and body size among all animals. The EQ is used as a rough estimate of the possible intelligence of an animal, with the idea being that a higher EQ indicates a larger brain than what would be expected for an animal of that size, and potentially more cognitive abilities.

The concept of the encephalization quotient was developed by Harry Jerison in the 1970s. He proposed that a larger brain size relative to body size could be linked to more complex behaviors and cognitive abilities. The EQ is particularly useful when comparing species with very different body sizes.

Humans have the highest known EQ, which is around 7, meaning that the human brain is seven times larger than what would be expected for an animal of our body size. Other animals with high EQs include dolphins and some great apes, which are also considered to be highly intelligent.

It's important to note that while EQ can be suggestive of cognitive potential, it is not a definitive measure of intelligence. Brain structure, the complexity of neural connections, and various other factors also play critical roles in determining an animal's cognitive capabilities. Additionally, EQ does not account for differences in intelligence within a species.