jumping spiders have some of the highest for an invertebrate, although some ant species have 14–15% of their mass in their brains, the highest value known for any animal. Sharks have one of the highest for fish alongside manta rays (although the electrogenic elephantfish has a ratio nearly 80 times higher—about 1/32, which is slightly higher than that for humans). Treeshrews have a higher brain to body mass ratio than any other mammal, including humans. Shrews hold about 10% of their body mass in their brain. It is a trend that the larger the animal gets, the smaller the brain-to-body mass ratio is. Large whales have very small brains compared to their weight, and small rodents like mice have a relatively large brain, giving a brain-to-body mass ratio similar to humans. One explanation could be that as an animal's brain gets larger, the size of the neural cells remains the same, and more nerve cells will cause the brain to increase in size to a lesser degree than the rest of the body. This phenomenon can be described by an equation of the form E =CSr, where E and S are brain and body weights, r a constant that depends on animal family (but close to 2/3 in many vertebrates), and C is the cephalization factor. It has been argued that the animal's ecological niche, rather than its evolutionary family, is the main determinant of its encephalization factor C. In the essay "Bligh's Bounty", Stephen Jay Gould noted that if one looks at vertebrates with very low encephalization quotient, their brains are slightly less massive than their spinal cords. Theoretically, intelligence might correlate with the absolute amount of brain an animal has after subtracting the weight of the spinal cord from the brain. This formula is useless for invertebrates because they do not have spinal cords, or in some cases, central nervous systems. Criticism Recent research indicates that, in non-human primates, whole brain size is a better measure of cognitive abilities than brain-to-body mass ratio. The total weight of the species is greater than the predicted sample only if the frontal lobe is adjusted for spatial relation. The brain-to-body mass ratio was however found to be an excellent predictor of variation in problem solving abilities among carnivoran mammals. In humans, the brain to body weight ratio can vary greatly from person to person; it would be much higher in an