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
Baleen whale the penis, which tapers toward the end, is called the "pars intrapraeputialis" or "terminal cone". The blue whale has the largest penis of any organism on the planet, typically measuring . Accurate measurements of the blue whale are difficult to take because the whale's erect length can only be observed during mating. The penis on a right whale can be up to – the testes, at up to in length, in diameter, and weighing up to , are also the largest of any animal on Earth. All baleen whales use sound for communication and are known to "sing", especially during