Brain size area in women, corresponding to spatial versus language specializations. Small studies have attempted to link brain volume with functional measures such as P300 auditory evoked potentials but finding no association. Studies attempting to related sibling differences in IQ to differences in brain volume are hampered by relatively small sample sizes and the noisy nature of such difference scores, yielding weak evidence for cross-trait cross-sib correlations. The largest brain is that of the sperm whale, weighing about , and killer whales, weighing about . An elephant's brain weighs just over and a bottlenose dolphin's . Brain size tends to vary according
Blue whale of its life, a blue whale calf drinks approximately of milk every day. Blue whale calves gain weight quickly, as much as every 24 hours. Even at birth, they weigh up to —the same as a fully grown hippopotamus. Blue whales have proportionally small brains, only about , about 0.007% of its body weight, although with a highly convoluted cerebral cortex. The blue whale penis is the largest penis of any living organism and also set the Guinness World Record as the longest of any animal's. The reported average length varies but is usually mentioned to have an average length