In general, smaller animals tend to have larger brains, measured as a fraction of body size. For mammals, the relationship between brain volume and body mass essentially follows a power law with an exponent of about 0.75. This formula describes the central tendency, but every family of mammals departs from it to some degree, in a way that reflects in part the complexity of their behavior.
Generally, smaller animals have larger brains relative to their body size. For mammals, the relationship between brain volume and body mass follows a power law with an exponent of about 0.75. This formula represents the average trend, but each family of mammals deviates from it in some way, which reflects their behavioral complexity.