It is a common belief that the size of the brain directly correlates to how intelligent an animal or person is. However, this is no exactly true. Scientists have indeed found some relationship between the size of a brain and the intelligence of an animal but the relationship is not very absolute. In fact, there are many human beings with large brains who are not super geniuses. Also, the comparison of brain size only holds true to some degree when comparing within the same species. If you compares brain size and intelligence across different types of animals, there is no relationship at all between brain size and intelligence. For example, human beings are generally thought to be much smarter than elephants, but an elephant’s brain is about 4 to 5 times heavier than a human being’s brain! Some scientists have started to study the sizes of different parts of the brain to try and determine if intelligence is controlled by any specific part of the organ. Thus far, there have not been any significant discoveries in such studies. The animal with the biggest brain is the sperm whale, which has a brain weighing in at 8 kg on average. Fruit-flies have the smallest brains in the world. Jelly fish on the other hand, have no brains at all! In fact, they do not have hearts either.