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
Right whale single female, suggesting that sperm competition is an important factor in mating behavior. Although the blue whale is the largest animal on the planet, the testes of the right whale are actually ten times larger than those of the blue whale – with each weighing up to , they are by far the largest of any animal on Earth. Gestation tends to last a year, and calves are born at in weight and in length. Weaning occurs after eight months. Right whales were a preferred target for whalers because of their docile nature, their slow surface-skimming feeding behaviors, their tendency