A measure of the relative size of the brain of a particular species compared with the expected value for members of the group to which it belongs. It is used to estimate the comparative intelligence of animals, particularly in anthropology. A logarithmic plot of brain mass against body mass for numerous representative species has a slope of roughly 3/4, which provides the baseline for calculating EQ values. The EQ corresponds to the distance above or below this line, and an EQ of 1 equates to the brain mass expected for the group. In mammals and birds the formula for calculating EQ is brain mass/0.12 × (body mass)0.66. Modern humans (Homo sapiens) have an EQ of roughly 6, meaning that their brain mass is six times greater than a typical mammal. Estimating EQ values is fraught with pitfalls, particularly when attempting to assess body mass from fragmentary fossil remains.
Subjects: Biological Sciences — Psychology.