In an edition of the Proceedings of the National Academy of Sciences published in 2001, researchers found that dolphins are able to recognize themselves in a mirror. The only other animals thought to be able to cognitively discern their own reflection are Humans, Great Apes, and Asian Elephants.
Bottlenose Dolphins (Tursiops truncatus) have an absolute brain mass of 1500-1700 grams. This is slightly greater than that of humans (1300-1400 grams) and about four times that of chimpanzees (400 grams) The brain to body mass ratio in dolphins is less than half that of humans: 0.9% versus 2.1%. This comparison appears more favourable if we leave aside the large amount of blubber (15-20% of mass) dolphins require for insulation. Humans have the highest brain-to-body ratio but there is debate whether dolphins or the treeshrew have the highest non-human animal brain-to-body ratio. [ripped from: wikipedia]
I think if humans are in charge of calculating the brain-to-body ratio, we’ll always have the best stats.