What Is an Encephalization Quotient?

The encephalization quotient (EQ) attempts to measure intelligence in animals by comparing brain mass to overall body mass. The EQ formula takes the total brain weight and divides it by the entire product of body weight multiplied by two constants. The constants take into account body volume and surface area.

The formula for an encephalization quotient does not take into account different individual weights. Instead, the formula assumes an average weight for the entire species. Otherwise, a human that weighs 300 pounds would have a different EQ than one who weighs 150 pounds. The formula also does not account for neuron density, cortical thickness or other structures of the brain. The EQ serves as a general way to externally measure intelligence.

Animals that have higher enchephalization quotients are smarter than those with lower figures. In general, mammals and birds have higher EQ figures than amphibians, reptiles and bony fish. Birds and mammals have brains 10 times larger than amphibians, reptiles and bony fish of the same size.

EQ numbers vary from species to species. The average human has an EQ of 6.56. The whale dolphin's EQ is 5.55. A chimpanzee's EQ is 2.63, whereas a coyote's is 1.69. The EQ of predatory mammals is generally higher than those of mammals that are prey.