Final answer:
The sperm whale's brain is about 40% to 73% heavier than an elephant's brain. While this indicates a larger brain size in sperm whales, it is their high cortical surface area that contributes to complex cognitive functions, not just the overall brain weight.
Step-by-step explanation:
A sperm whale's brain is significantly larger than an elephant's. The average brain weight of a sperm whale is about 7.8 kilograms, while an African elephant's brain typically weighs around 4.5 to 5.5 kilograms, making the sperm whale's brain approximately 40% to 73% heavier than an elephant's brain. In the animal kingdom, brain size is not always indicative of intelligence or dominance, as demonstrated by humans who have smaller brains than elephants but have managed to utilize their cognitive abilities to enchain and employ elephants.
The larger brain size in whales is partly attributed to the high surface area of the cerebral cortex, which is associated with advanced cognitive functions and complex social behaviors. This increase in brain size is especially pronounced in apes, whales, and dolphins and is considered a factor in the evolution of complex behaviors unique to these mammals.