how do dolphins know when a human or an animal is in danger? the dolphin's brain structure may help eplain this. the dolphin's brain is very heavyn . it is 25 percent heavier than a human brain. it is also very large in comparison to the size of the dolphin itself. humans have three separate areas of the brain,but dolphins have four. in humans,the senses are divided between two areas of the brain. in dolphins,the fourth area controls all the senses. scientists don't yet understand much about the dolphin brain. perhaos having all of the senses in one part of the brain means dolphins are more aware of everything around them, including danger to others.